Bosch C1210ESC, C1210ES, C1050ES, C950ES, 940ES Technical Service Bulletin

Technical Service Bulletin:

C6 & C7 Error Code Troubleshooting

Models: C1210ESC, C1210ES, C1050ES, C950ES, 940ES, 940ESO, 830ES, 2400ES,

2700ES, 715ES, C800ES, C920ES/ESC, Integra 500, Evolution 500

Introduction

This procedure must be performed by a qualifi ed technician.

DANGER!

120 VAC present in wire connections. Use caution
when testing.

Follow the procedures below and report results to Bosch Technical
Support. This will assist in determining the cause and solution to the
problem.

C6 and C7 error codes

These errors are fan-related error codes with the following
explanations:

 C6 error indicates the primary fan rotation is too low during

operation.

 C7 error indicates there is no primary fan rotation sensed

during an attempted start-up.

Primary Fan Assembly

 The primary fan is a 120 volt AC fan that receives power from

the main control board.

 The primary fan has its own built-in circuit board which relays

information and signals back to the control board.

Tools needed:

 Phillips head screwdriver
 Digital Multi-meter

3. Ensure that the 3 foot minimum separation between air intake
and exhaust vents is met (applies to a twin pipe vent system).

4. Verify the heater is plugged into a properly grounded 120V AC
power supply.

5. Supply the heater with a steady supply voltage. It is
recommended to supply electricity from a dedicated electrical
circuit with no other major appliances on the same circuit.

6. Shut off power to the heater and unplug from electrical outlet.

Remove cover per installation manual.

7. Remove the black plastic intake (Fig.1, pos.1) that is secured

with three Phillips head screws to the fan (Fig.1, pos.2).

Figure 1

Procedure

1. Press the reset button on the control panel of the heater to
attempt to clear the error code. If the error code does not reset
or continues to reoccur, proceed with the following trouble­shooting steps.

2. Confi rm that the exhaust vent is not blocked and does
not exceed the specifi ed maximum length as shown in the
installation manual.

8. Check the wire connection to the fan. The wire connection is

located on the back, left hand side of the fan housing. (Fig. 2).

2 | C6 & C7 Error Code Troubleshooting

Technical Service Bulletin

Figure 2

9. Check that the wire connections to the control board are fi rmly

attached to the board. Removal of the lower access cover on

the control board is required. Refer to Bulletin TWH-G3-24.

10. Remove wire connection from back of fan, plug in heater and

turn power on with water shut off. Check for voltage AC on the

plug between the 1st and 2nd pin. You should fi nd 120VAC (Fig.

3)

Figure 3

Figure 4

Figure 5

a. If the plug shows 120 VAC between the pins, the

primary fan needs to be replaced.

b. If the plug shows no voltage between the pins; shut

power off, disconnect plug from the outlet, and check
the 2.5A white fuse inside of the control unit (Fig. 4).
Refer to Bulletin TWH-G3-24. If the 2.5A white fuse has
continuity, then the control unit needs to be replaced.

c. If the 2.5A fuse is blown, replace with spare from the

back cover of the control unit, remove the connection
from the primary fan, and remove both wire connections
from the secondary fan (Fig. 5).

d. Reconnect primary fan only, turn power on, run

water for 30 seconds. LEAVE SECONDARY FAN
DISCONNECTED

Data subject to change without notice | Printed in the USA | BTC 740002330 A | 05.2014

e. If fan turns on, unit ignites, and/or E4, then shut the

power off and reconnect the secondary fan. If C6 or C7
and/or the fuse blows before connecting the secondary
fan then the primary fan needs to be replaced.

f. With both primary and secondary fans connected, turn

power on, and run water. If no issues, then just a bad
fuse. If the 2.5A fuse blows then the secondary fan
needs to be replaced.

After completing this procedure, please call us while still at

the unit at 1-800-798-8161 for diagnosis and resolution. If
it is more convenient for you, please email the results of
this procedure to [e-mail] and we will reply
within one business day.

Bosch Thermotechnology Corp.
50 Wentworth Avenue
Londonderry, NH 03053

Tel: [phone]
Fax: [phone]
www.bosch-climate.us

Bosch Thermotechnology Corp.