Webasto Air Top 2000 ST D Service And Repair Manual

Air Heater

Air Top 2000 ST D (Diesel)
Air Top 2000 ST B (Gasoline)

Service and Repair Manual

– Improper installation or repair of Webasto heating and cooling systems can cause

fire or the leakage of deadly carbon monoxide leading to serious injury or death.

– Installation and repair of Webasto heating and cooling systems requires special

Webasto training, technical information, special tools and special equipment.

– NEVER attempt to install or repair a Webasto heating or cooling system unless you

have successfully completed the factory training course and have the technical skills,
technical information, tools and equipment required to properly complete the
necessary procedures.

– ALWAYS carefully follow Webasto installation and repair instructions and heed all

WARNINGS.

– Webasto rejects any liability for problems and damage caused by the system being

installed by untrained personnel.

AIR TOP 2000 ST TABLE OF CONTENTS

Contents Page

1. Introduction 1

1.1 Contents and Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.1.1 Use of the Air Heaters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.2 Meaning of Signal Words . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

1.3 Additional Documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.4 Safety Information and Regulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

1.4.1 Statutory Regulations and Safety Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

1.4.2 General Safety Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

1.5 Suggestions for Improvements and Changes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

2. General Description 5

2.1 Drive Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5

2.2 Heat Exchanger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2.3 Burner Insert with Combustion Pipe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2.4 Control Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2.5 Flame Sensor (Gasoline Heaters Only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2.6 Ceramic Glow Pin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2.7 Overheating Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2.8 Fuel Metering Pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

3. Functional Description 9

3.1 Control Element (Rheostat). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

3.2 Switch On. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

3.3 Heating Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

3.4 Control Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

3.5 Control Pause. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

3.6 Switch Off . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10

3.7 Fault Lock-out. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10

3.7.1 Error Monitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11

3.7.2 Reset a Fault Lock-out . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

4. Technical Data 13

5. Troubleshooting 15

5.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

5.2 General Error Symptoms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15

5.3 Error Symptoms during Function. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

5.4 Error Code Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17

6. Functional Tests 21

6.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

6.2 Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21

6.2.1 Setting the CO2 Content . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

6.3 Testing Individual Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

6.3.1 Ceramic Glow Pin Resistance Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

6.3.2 Resistance Test on Flame Sensor (gasoline heaters only). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21

6.3.3 Overheating Sensor Resistance Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

7. Circuit Diagrams 23

7.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

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TABLE OF CONTENTS AIR TOP 2000 ST

8. Servicing Work 27

8.1 General. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27

8.2 Work on the Heater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27

8.3 Work on the Vehicle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27

8.4 Heater Trial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27

8.5 Servicing Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27

8.6 Visual Inspections and Installation Instructions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27

8.6.1 Hot Air System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27

8.6.2 Fuel Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28

8.6.2.1 Fuel Extractor (Standpipe) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28

8.6.2.2 Fuel Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30

8.6.3 Fuel Metering Pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30

8.6.3.1 Installation Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30

8.6.3.2 Installation and Attachment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30

8.6.4 Fuel Filter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30

8.6.5 Combustion Air Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31

8.6.6 Exhaust Line . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31

8.6.7 Combustion Air Inlet and Exhaust Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31

8.6.8 Electrical Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32

8.6.8.1 Heater Connection, Control Element. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32

8.6.8.2 Supply Voltage Connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32

8.6.8.3 Control Element (Rheostat) Connection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32

8.7 Removal and Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34

8.7.1 Heater, Removal and Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34

8.7.1.1 Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34

8.7.1.2 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34

8.8 Start-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34

9. Repair 35

9.1 General. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35

9.1.1 Work on Stripped-down Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35

9.1.1.1 Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35

9.1.1.2 Visual Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35

9.1.2 Remove the Casing Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36

9.1.2.1 Installation of an External Temperature Sensor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35

9.2 Dismantling and Assembling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36

9.2.1 Remove the Casing Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36

9.2.1.1 Cover for Electrical Connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36

9.2.1.2 Grates for Hot Air Inlet and Outlet. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36

9.2.1.3 Cover for Hot Air Inlet and Outlet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36

9.2.1.4 Top Shell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36

9.2.1.5 Bottom Shell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36

9.2.2 Fit the Casing Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36

9.2.2.1 Bottom Shell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36

9.2.2.2 Top Shell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36

9.2.2.3 Cover for Hot Air Inlet and Outlet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36

9.2.2.4 Grates for Hot Air Inlet and Outlet. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36

9.2.2.5 Cover for Electrical Connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36

9.2.3 Changing the Control Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38

9.2.3.1 Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38

9.2.3.2 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38

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AIR TOP 2000 ST TABLE OF CONTENTS

9.2.4 Changing the Overheating Sensor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

9.2.4.1 Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38

9.2.4.2 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38

9.2.5 Changing the Combustion Air Fan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

9.2.5.1 Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38

9.2.5.2 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38

9.2.6 Changing the Flame Sensor (gasoline heaters only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

9.2.6.1 Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39

9.2.6.2 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39

9.2.7 Changing the Ceramic Glow Pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41

9.2.7.1 Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41

9.2.7.2 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41

9.2.8 Changing the Burner Insert, Combustion Pipe and the Heat Exchanger . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43

9.2.8.1 Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43

9.2.8.2 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43

10.Product Information 45

www.webasto.us III Webasto Product N.A., Inc.

AIR TOP 2000 ST INTRODUCTION

1. INTRODUCTION

1.1 CONTENTS AND PURPOSE

This repair shop manual is intended to assist trained
personnel with repairing both the gasoline and the diesel
versions of the Air Top 2000 ST air heaters.

1.1.1 USE OF THE AIR HEATERS

The Webasto Air Top 2000 ST air heaters are designed

– to heat cabins, boats, trucks, minibuses, vans,

ambulances and motor homes.

– to defrost vehicle windows.

They are not designed for heating cargo areas used to
carry hazardous substances.

The heaters operate independently of the engine and are
connected to the fuel tank and the electrical system of
the vehicle.

They are not designed for installation in vehicles with
water or air-cooled engines.

1.3 ADDITIONAL DOCUMENTATION

This workshop manual contains all the information and
instructions required for repairing Air Top 2000 ST air
heaters. The use of additional documentation is not
normally required. If necessary, the operating /
installation instructions and the installation suggestion
for the specific vehicle may also be used.

1.4 SAFETY INFORMATION AND REGULATIONS

In principle, the general accident prevention regulations
and current works safety instructions are applicable.

The “General safety regulations” that go beyond the
scope of the above regulations are stated below
(see 1.4.2).

Any special safety regulations relevant to this instruction
manual will be highlighted in the relevant sections or text
passages of the procedures.

1.4.1 STATUTORY REGULATIONS AND SAFETY
I

NSTRUCTIONS

1.2 MEANING OF SIGNAL WORDS

Throughout this manual, the signal words DANGER,
WARNING, CAUTION, and NOTE have the following
meanings:

DANGER: This heading and text style is
used to highlight that non-compliance with
instructions or procedures will cause
injuries or lethal accidents to personnel.

WARNING: This heading and text style is
used to highlight that non-compliance with
instructions or procedures may cause
injuries or lethal accidents to personnel.

CAUTION: This heading and text style is
used to highlight that non-compliance with
instructions or procedures may cause
damage to equipment.

NOTE: This heading and text style is used to

highlight and draw attention to information we
feel you would like to have. It could have to do
with procedures and tips that will help you work
more efficiently.

NOTE: The provisions of these Directives are
binding within the United States of America by
FMCSA Directive 393.77 and should similarly be
observed in countries without specific
regulations.

Extract from the Federal Motor Carrier Safety
Administration

Part 393: Parts and Accessories Necessary for Safe
Operation

§393.77 Heaters

(b)(15) Certification required.

Every combustion type heater, shall be marked plainly to
indicate the type of service for which such heater is
designed and with a certification by the manufacturer
that the heater meets the applicable requirements for
such use. For example, "Meets FMCSA Bus Heater
Requirements.”

1.4.2 GENERAL SAFETY INFORMATION

The mouth of the exhaust pipe should be installed
upwards, to the side or, if the exhaust pipe passes under
the floor of the vehicle, to the side or rear limit of the
driver’s cab or the vehicle.

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The function of important parts of the vehicle must not
be adversely affected. It must not be possible for
condensate or water to collect in the exhaust pipe. Drain
holes may be used.

INTRODUCTION AIR TOP 2000 ST

The electric cables and controls for the air-conditioning
system must be arranged in the vehicle so that their
proper functioning cannot be adversely affected in
normal operating conditions.

The following points for the installation of fuel lines and
the installation of additional fuel tanks must be observed.

• Fuel pipes must be designed in such a way that
torsion in the vehicle, movements by the engine and
the like do not have a negative effect on their
durability. They must be protected from mechanical
damage.

• Parts that carry fuel must be protected from heat
that will adversely affect their function and
positioned so that dripping or evaporating fuel
cannot collect or ignite on hot parts or on electrical
equipment.

• The fuel lines (Mecanyl hose) must not be
immediately next to the exhaust pipe and must be
thermally insulated if necessary, otherwise they will
pose a fire risk.

• All pipes that come into contact with fuel must have
sealed connections, they must not be damaged in
any way and the must be checked at regular intervals
(at least the same intervals as for inspection of the
vehicle as a whole).

NOTE: If any damage or leaks are found on
the fuel line, the heater must not be used until
the damage has been rectified by an authorized
Webasto workshop.
Put the heater out of action by removing the
fuse.

Installation regulations for Webasto fuel tanks for
supplying fuel to heaters in vehicles:

• The tank must not be installed in the passenger or
driver’s cabin of buses.

• The fuel filler neck must not be inside the passenger
or driver’s cabin in any vehicle.

• Fuel tanks for normal or super grades of petrol must
not be immediately behind the front trim of the
vehicle. They must be separated from the engine in
such a way that in the event of an accident the fuel
will not be expected to ignite. This does not apply to
tractor units with an open driver’s seat.

The air heater’s heat exchanger can be used for a
maximum of 10 years and must then be replaced by the
manufacturer or one of its authorized workshops using a
genuine spare part. A label must then be affixed to the
heater showing the date of sale and the wording
“Genuine spare part”.

When you change the heat exchanger it is essential that
you also replace the overheating protection element
(overheating sensor) to prevent possible function faults
caused by using the old overheating sensor.

The Air Top 2000ST air heaters are prepared for interior
installation and sealing directly on the cabin floor or a
cabin wall. Non-release connections must be used in the
interior for combustion air and exhaust pipes with the
accessories available from Webasto.

The seal between the heater mounting and the vehicle
floor must always be installed; otherwise harmful
emissions may get into the interior of the vehicle.

The hot and combustion air intake openings must be
positioned in such a way that no water can ingress into
them if the vehicle drives through a water hazard for
which it has been approved.

For passenger carrying vehicles such as shuttle busses,
transit busses, and coaches, where the heater is to be
installed in the passenger cabin, a protective cover or
installation box should be installed over the heater to
prevent contact with hot surfaces by passengers and
heat sensitive objects.

The protective cover or installation box must have
sufficient external ventilation to ensure that a maximum
temperature of 40°C (104°F) is not exceeded in the box.
Malfunctions may occur if the temperature exceeds this
level.

The heater must be switched off at filling stations and
fuel tank farms because of the risk of explosion.

Wherever inflammable vapors or dust may form (for
example near fuel, coal, wood dust or cereal stores or the
like), the heater must be switched off because of the risk
of explosion.

The heater must not be operated in enclosed areas, such
as garages or workshops without an exhaust emissions
extraction system, not even using the timer, because of
the risk of asphyxiation and poisoning.

In the event of lengthy heavy smoke development,
unusual combustion noise or a smell of fuel, the heater
must be put out of action by removing the fuse and must
not be started again until it has been examined by
Webasto-trained personnel. Liability claims can only be
lodged if the claimant can prove that he has complied
with the servicing and safety instructions.

Overheating

Keep hot air inlet and hot air outlet free of dirt and other
items. Dirty, blocked air lines can cause the heater to
shut down due to overheating.

After an overheating lock-out, check that the air system
is clear, remove any materials that may block the air flow
and have any damage to the air lines repaired by an

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AIR TOP 2000 ST INTRODUCTION

authorized Webasto workshop. After this the heater
lock-out can be cancelled by switching it off and then on
again. If this action does not produce the required
success (if the heater overheats again) take it to a
Webasto-authorized workshop. Never remove the
grating over the air inlet of the heater.

The air outlet jets or air vents with adjustable flaps must
always be opened to some extent so that the air flow
through the heater is not completely blocked. At least
one air vent must be prevented from being closed.

If the heater is installed in a storage area, you must
ensure that no inflammable substances are kept in this
area and that other material does not restrict the air
supply to the heater.

Air lines must be securely fixed to the heater (using pipe
clips, for example) and all other connection points (for
example vents).

IMPORTANT! The errors described below are to
be avoided at all costs:

• Do not stand on the heater or place or throw any
heavy objects on the heater.

• Do not place any items of clothing, textiles or similar
materials over the heater or in front of the hot air
inlet side and hot air outlet.

• The flow of hot air from the heater must not be
restricted or blocked by highly inflammable
substances or materials such as rags, cleaning wool,
etc.

• Inflammable or explosive substances and gases must
not be placed near or in contact with the heater, the
hot air line, the flow of hot air or the exhaust pipe.

• The heater must not be cleaned with a high pressure
cleaner.

• Do not switch the heater off at the main battery
switch or battery isolation switch since otherwise it is
possible that it may suffer long term damage if it is
switched off frequently using the battery isolation
switch and this can cause damage and negative
influences on the function of the heater.

NOTE: Failure to follow the installation
instructions and the notes contained therein will
lead to all liability being refused by Webasto
The same applies if repairs are carried out
incorrectly or with the use of parts other than
genuine spare parts. This invalidates the type
approval for the heater and its homologation /
EC type permit.

You must read the operating manual before starting the
heater for the first time.

1.5 SUGGESTIONS FOR IMPROVEMENTS AND

CHANGES

Complaints, improvement suggestions or corrections
relating to this workshop manual should be addressed to

Webasto Product North America, Inc.
Technical Documentation Group
15083 North Road
Fenton MI 48430

Phone: [phone]

Fax: [phone]

www.webasto.us 3 Webasto Product N.A., Inc.

AIR TOP 2000 ST GENERAL DESCRIPTION

2. GENERAL DESCRIPTION

The Air Top 2000 ST air heater is based on the evaporator
principle and essentially consists of the following:

– the drive unit with a combustion and hot air blower
– the heat exchanger
– the burner insert with combustion pipe
– the control unit

Figure 2: Air Top 2000 ST Air Heater without Casing

Figure 1: Air Top 2000 ST Air Heater

To control and monitor it, the heater has

– a control unit with temperature sensor
– a flame sensor (gasoline heaters only)
– a ceramic glow pin
– an overheating sensor

inside it.

All Air Top 2000 ST heaters can also be controlled using
an external temperature sensor.

The fuel supply is provided from an external source using
a metering pump.

If a fault occurs, an error code will be output in the
display of the combination or standard timer. If the
heater has a control element, the ON control light will
flash.

2.1 DRIVE UNIT

The drive unit consists of the drive motor, the
combustion air blower, the heat air blower and the
intake casing.

The combustion air blower supplies the air required for
the combustion process from the combustion air inlet to
the burner insert.

The removable hot air blower transports the hot air from
the hot air inlet via the heat exchanger to the hot air
outlet.

In addition, the heater can be checked using a personal
computer (see PC heater diagnostic operating manual).

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Figure 3: Drive Unit

GENERAL DESCRIPTION AIR TOP 2000 ST

Burner insert

Combustion
pipe

Internal
temperature sensor

Wiring
harness

Component
plug sockets

2.2 HEAT EXCHANGER

The heat generated by the combustion process is
transferred to the air transported by the combustion and
hot air blowers in the heat exchanger.

2.4 CONTROL UNIT

The control unit is the central component for ensuring
the function is maintained and for monitoring the
heater’s operation. A temperature sensor in the control
unit is designed to control the room temperature. An
external temperature may also be connected to all the
heaters.

If a fault occurs, an error code will be output in the
display of the combination timer. If the heater has a
control element, the ON control light will flash.

In addition, the heater can be checked using a personal
computer (see PC heater diagnostic operating manual).

Figure 4: Heat Exchanger

2.3 BURNER INSERT WITH COMBUSTION PIPE

The fuel is distributed over the burner cross-section in the
combustion pipe in the burner insert. The mixture of fuel
and air burns in the combustion pipe, thus causing the
heat exchanger to become hot.

Figure 6: Control Unit

2.5 FLAME SENSOR (GASOLINE HEATERS ONLY)

The flame sensor is a low-ohm PTC resistor, which
changes its resistance depending on the heat emitted by
the flame.

This change in resistance is analyzed by the control unit
so that the flame status is monitored whenever the
heater is operating.

Figure 5: Burner Insert with Combustion Pipe

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Figure 7: Flame Sensor

AIR TOP 2000 ST GENERAL DESCRIPTION

2.6 CERAMIC GLOW PIN

The mixture of fuel and air is ignited by the glow plug
when the heater is started. The glow pin takes the form
of an electrical resistor and is positioned in the burner
insert on the side away from the flame.

2.7 OVERHEATING SENSOR

The overheating sensor measures the temperatures in the
rib area of the heat exchanger whenever the heater is
operating. The control unit evaluates the signal and
protects the heater from hot air outlet temperatures
above 150 °C and surface temperatures above 80 °C by
shutting down the combustion process and blowing cold
air over the heater.

The heater then suffers a fault lock-out and can be
restarted by being switched off and then on again (see

3.2).

Figure 8: Ceramic Glow Pin

Figure 9: Overheating Sensor

2.8 FUEL METERING PUMP

The metering pump is a combined transport, metering
and shut-off system for supplying fuel from the vehicle’s
tank to the heater.

Figure 10: Fuel Metering Pump DP 30.2/3 (with Damper)

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AIR TOP 2000 ST FUNCTIONAL DESCRIPTION

3. FUNCTIONAL DESCRIPTION

3.1 CONTROL ELEMENT (RHEOSTAT)

The control element is designed to switch the heater on
and off, adjust the required room temperature (intake
temperature between 5 °C and 35 °C) and to reset the
heater after a fault.

The green LED serves as the On indicator (LED
permanently lit up) and as a fault signal (LED flashes).

3.2 SWITCH ON

Set the control element to the required temperature.

If the hot air temperature is lower than the nominal
temperature, the heater will start.

NOTE: If the temperature of the hot air intake
is above the set nominal temperature, only the
motor for the hot and combustion air blower
will start (control pause). Special feature: The
control pause speed is 0 rpm if boat heaters are
used.

The function of the flame sensor is checked. If
the flame sensor now reports “light”, the
system will attempt to cool the flame sensor for
60 seconds. If the flame sensor still reports
“light” the control unit will suffer a fault lock­out. If another monitored component has
suffered a fault, the fault lock-out will take
effect without any slow down time.

Start

When the heater is switched on, the ON signal light will
be lit and the glow plug will be switched on (cycled). The
motor for the hot and combustion air blower will be set
to approx. 50% of its maximum speed.

After approx. 40 seconds the fuel metering pump will
start, and the flame formation will begin. To improve the
starting quality the metering pump and combustion air
blower are started with different frequencies and speeds.
After a further 95 seconds (gasoline) or 110 seconds
(diesel) the glow pin will be switched off and the
existence of the flame established.

Automatic Restart

If no flame is detected, the starting procedure will be
repeated. The glow plug will be switched on again
(cycled). The motor for the hot and combustion air
blower will be set to approx. 25% of its maximum speed.

After approx. 30 seconds (petrol) or 50 seconds (diesel)
the fuel metering pump will start, and the flame
formation will begin. After a further 65 seconds (petrol)
or 90 seconds (diesel) the glow plug will be switched off
and the existence of the flame established.

If the heater has again failed to ignite properly, the
heater will be shut down using a fault slow down
procedure at maximum speed after 180 seconds and will
suffer a fault lock-out.

NOTE: After a restart the heater will suffer a
fault lock-out. To reset the fault switch the
heater off briefly (min. 2 seconds) and switch
back on.

3.3 HEATING MODE

While the heater is operating, the combustion gases pass
through the heat exchanger. During this process the
combustion heat is given off to the walls of the heat
exchanger, absorbed by the hot air transported by the
hot air blower and fed into the interior of the vehicle.

The temperature of the hot air intake is measured by a
temperature sensor on the intake side of the heater or an
external temperature sensor. If the measured
temperature is lower than the value set on the control
element, the output of the heater is increased to
maximum heat output.

To increase the burner service life when it is used
continuously the transport capacity of the metering
pump is reduced for 10 seconds every 10 minutes.
In addition, heating mode is interrupted every 8 hours in
the same way as for a control pause.

3.4 CONTROL MODE

In control mode the blower speed and the metering
pump delivery rate are dependent on the heat output.
The glow pin is switched off.

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FUNCTIONAL DESCRIPTION AIR TOP 2000 ST

3.5 CONTROL PAUSE

After the temperature set on the control element has
been reached, the heat output is reduced. The speed of
the heating and combustion air blower and the delivery
rate of the metering pump are reduced.

If, at minimum heat output, the intake temperature set
on the control element is exceeded, the metering pump
is shut down and the combustion process ended. To
burn off the flame properly the blower speed falls after
20 seconds to low-fire rate speed and then returns to the
initial speed after 15 seconds, after which it falls to the
control pause speed in 3 minutes, where it remains for
the entire control pause.

The control pause speed on boat heaters is 0.

If the temperature set on the control element is not
observed at the temperature sensor, the heater will
restart.

NOTE: Changes to the setting on the control
element are implemented by the control unit
and heater after a delay.

3.6 SWITCH OFF

3.7 FAULT LOCK-OUT

The control unit has identified errors on individual heater
components and faults during the starting procedure and
in operation. The heater is switched off and goes into
fault lock-out if the following conditions occur:

• No repeated or incorrect start

• Temperature sensor defective

• Overheating sensor interrupt or short circuit

• Overheating sensor installed incorrectly

• Glow pin interrupt or short circuit

• Blower motor overload or blocked or short circuit or
break

• Flame sensor interrupt or short circuit

• Error in the metering pump or overheating guard
circuit (start phase only)

• Under voltage below 10.5 V / 21 V for longer than
20 seconds

• Over voltage above 16 V / 32 V for longer than 6
seconds

• Control module defective

When the heater is switched off, the ON control LED on
the control element goes out. If no fuel has been
transported or if the heater is in the control pause, the
heater is switched off immediately without a slow down
time.

If the fuel transport has been started, it is ended
immediately when the heater is switched off. The heater
is switched off using the same method as the transition
from control mode to control pause. The device is then
switched off automatically.

NOTE: The heater may be switched on again
during the slow down time. In this case the
slow down time is completed and the heater is
then restarted.

The fuel supply is stopped if the heater overheats. The
heater continues to run in the same way as if it is
switched off manually. After it stops the control unit will
be set to fault lock-out. After the slow-down phase the
control module is set to fault lock-out if the overheating
counter is greater than the value programmed in the
data record (currently 20).

The overheating is indicated by the indicator flashing
10 times.

Rectify the cause of the fault.

To reset the fault, switch the heater off briefly (at least
2 seconds) and then on again.

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AIR TOP 2000 ST FUNCTIONAL DESCRIPTION

3.7.1 ERROR MONITOR

The overheat, incorrect start and flame failure errors are
counted and cause the heater to suffer a fault lock-out
after an error has occurred the maximum number of
times.

The incorrect start counter FSZ is incremented by 1 each
time the heater fails to start and decremented by 1 each
time it starts correctly, but does not fall below 0. If the
incorrect start counter reaches its maximum value of 7,
the heater will go into the heater lock-out status HGV.

The error counter SZ is incremented by 1 with each error
for which there is no separate counter. The error counter
is reset to 0 at the start of control mode. If the error
counter reaches its maximum value of 10, the heater will
go into the heater lock-out status HGV.

The overheating counter ÜHZ is incremented by 1 each
time the heater overheats. If the overheating counter
reaches its maximum value of 20, the heater will go into
the heater lock-out status HGV.

The flame failure counter FAZ is increased by 1 each time
the flame fails during heating mode. The counter is
decremented by 1 each time the heater is in control
mode.

If the FAZ reaches a value of 6, the heater will go into
fault lock-out mode and the permanent flame failure
counter FAZP will be incremented by 1. In control mode
the permanent flame failure counter FAZP will be
decremented by 1. When the heater is burning properly
again, the FAZP will return to 0 after a few control cycles.
If the permanent flame failure counter exceeds its
maximum value of 6, however, the heater will go to
permanent heater lock-out status (error code F13).

3.7.2 RESET A FAULT LOCK-OUT

The various fault lock-outs can be reset as follows.

Fault lock-out: Switch heater off using the

control element and then on
again after more than 2 sec.

Heater fault lock-out: Remove the fuse and reinsert it

Permanent heater
fault lock-out: Delete the error with the

PC diagnostic tool

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AIR TOP 2000 ST TECHNICAL DATA

4. TECHNICAL DATA

Except where limit values are specified, the technical data
listed in the table refer to the usual heater tolerances of
±10% at an ambient temperature of +20 °C (+68 °F) and
at the rated voltage and in rated conditions.

Electrical components:

The control unit, combustion air blower (drive), metering
pump, timer, glow plug and control element are
designed for 12 V or 24 V.

The components temperature sensor and flame monitor
(only petrol heater) are not designed for a specific
voltage.

Fuel for Air Top 2000 ST B (gasoline):

The fuel specified by the manufacturer must be used.

HEATER Operation AT 2000 ST B AT 2000 ST D

Typ e Te st Pe r mi t EM C

Heater
Model Air heater with evaporator burner
Heat Output kW

Btu/h

Fuel Gasoline Diesel #1, #2, Arctic, PME

Fuel Consumption l/h

gal/h – US
Rated Voltage 12 V 12 V 24 V
Operating Voltage Range V 10.5 - 16 V 10.5 - 16 V 21 - 32 V
Rated Power Consumption Control Range 14 - 29 Watts
Maximum Ambient Temperature:

Heater -operation

-warehouse

Dosing Pump -operation

-warehouse

Control Element -operation

-warehouse
Max. Combustion Air Inlet Temperature –40 °C... +20 °C (–40 °F... +68 °F)
Adjustment Range For Interior

Temperature
Delivery Rate For Hot Air At Fan Speed against 0.5 mbar

Co

In Exhaust Gas

2

(permanent function range)
Heater Dimensions

Length X Width X Height
Weight Of Heater 2.6 kg (5.73 lb)

Control Range 1.0 - 2.0 kW

Control Range 0.14...0.27

Control Range +5 °C... +35 °C (+41 °F... +95 °F)

against .00725 PSI

1 kW
2 kW

Fuel for Air Top 2000 ST D (diesel/PME):

The diesel fuel specified by the vehicle manufacturer
must be used.

We know of no negative influences due to additives.

If fuel is extracted from the vehicle’s tank, follow the
additive instructions issued by the vehicle manufacturer.

If you change to low-temperature fuel, the heater must
be operated for approx. 15 minutes so that the fuel
system is filled with the new fuel.

The Air Top 2000 ST D heater is also licensed for use with
PME (bio-diesel), which complies with ASTM D6751 and
DIN EN 14214.

e1*72/245*95/54*1085*--

e1*2001/56*0022*--

0.9 - 2.0 kW

3415 - 6830

0.037...0.071

–40 °C... +40 °C (–40 °F... +104 °F)
–40 °C... +85 °C (–40 °F... +185 °F)

–40 °C... +20 °C (–40 °F... +68 °F)
–40 °C... +85 °C (–40 °F... +185 °F)
–40 °C... +75 °C (–40 °F... +167 °F)
–40 °C... +85 °C (–40 °F... +185 °F)

Max. 93 m

Max. 55 cfm at 4750 rpm

5.0... 8.0

9.0... 12.5

311 mm L X 120 mm W X 121 mm H

12.25 in L X 4.72 in W X 4.76 in H

3

/h at 4750 rpm

3074 - 6830

and Kerosene

0.12...0.24

0.032...0.063

5.0... 8.0

9.0... 12.5

Table 1. Technical data

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