Bendix Commercial Vehicle Systems D-2 User Manual

Bendix® D-2® Governor

SD-01-503

COVER

EXHAUST

PORT

UNLOADER

PORTS (3)

RESERVOIR

PORTS (3)

RETAINING RING

PRESSURE SETTING

SPRING

19 LOWER

SPRING SEAT

SPRING GUIDE

19 LOWER

SPRING SEAT

8 O-RING

12 O-RING

MOUNTING

HOLES

(2)

O-RING

INLET/EXHAUST

VALVE SPRING

FIGURE 1 - D-2® GOVERNOR

UPPER SPRING

SEAT

EXHAUST

STEM

INLET/EXHAUST

VALVE

ADJUSTING

SCREW

RETAINING

RING

LOCKNUT

BODY

PISTON

RETAINING

PISTON

FILTERS

RING

EXHAUST

STEM

SPRING

WASHER

RETAINING

O-RING

INLET/EXHAUST

VALVE

INLET/EXHAUST

COVER VALVE

SPRING

RING

BLUE

NONMETALLIC

O-RING

CLEAR/BLACK NONMETALLIC

WITH O-RING

BLACK

RUBBER

FIGURE 2 - TYPES OF COVERS

DESCRIPTION

The Bendix® D-2® governor, operating in conjunction with the unloading mechanism, automatically controls the air pressure in the air brake or air supply system between a maximum (cut-out) pressure and a minimum (cut-in) pressure. The compressor runs continually while the engine runs, but the actual compression of air is controlled by the governor actuating the compressor unloading mechanism which stops or starts the compression of air when the maximum or minimum reservoir pressures are reached.

NONMETALLIC METALLIC

FIGURE 3 - TYPES OF PISTONS

D-2® governors are provided with mounting holes which allow direct mounting to the compressor or remote mounting.

Porting consists of three reservoir ports (1/8 inch P.T.), three unloader ports (1/8 inch P.T.) and one exhaust port (1/8 inch P.T.).

OPERATION

Reservoir air pressure enters the D-2® governor at one of its reservoir ports and acts on the piston and inlet/exhaust valve. As the air pressure builds up, the piston and valve move together against the resistance of the pressure setting spring. When the reservoir air pressure reaches the cut-out setting of the governor, the exhaust stem seats on the inlet/exhaust valve, closing the exhaust passage, and then opens the inlet passage. Reservoir air pressure then ﬂ ows around the inlet valve, through the passage in the piston and out the unloader port to the compressor unloading mechanism. Air also ﬂ ows around the piston which is slightly larger at the upper end. The added force resulting from this larger area assures a positive action and fully opens the inlet valve.

As the system reservoir air pressure drops to the cutin setting of the governor, the force exerted by the air pressure on the piston will be reduced so that the pressure setting spring will move the piston down. The inlet valve will close and the exhaust will open. With the exhaust open, the air in the unloader line will escape back through the piston, through the exhaust stem and out the exhaust port.

Never condemn or adjust the governor pressure settings unless they are checked with an accurate test gauge or a dash gauge that is registering accurately. If the pressure settings of the D-2® governor are inaccurate or it is necessary that they be changed, the adjustment procedure follows. Note: If the governor cover is marked nonadjustable and the adjusting stem has been sheared off, this is a non-serviceable governor and must be replaced with a new or remanufactured unit.

A. Remove the top cover from the governor. B. Loosen the adjusting screw locknut. C. To raise the pressure settings, turn the adjusting screw

counter-clockwise. T o lower the pressure settings, turn the adjusting screw clockwise. Note: Be careful not to over adjust. Each 1/4 turn of the adjusting screw raises or lowers the pressure setting approximately 4 psi.

D. When proper adjustment is obtained, tighten the

adjusting screw locknut and replace the cover.

(Note: The pressure range between cut-in and cut-out is not adjustable.)

PREVENTIVE MAINTENANCE

Important: Review the Bendix Warranty Policy before

performing any intrusive maintenance procedures. A warranty may be voided if intrusive maintenance is performed during the warranty period.

No two vehicles operate under identical conditions, as a result, maintenance intervals may vary. Experience is a valuable guide in determining the best maintenance interval for air brake system components. At a minimum, the D-2® governor should be inspected every 6 months or 1500 operating hours, whichever comes first, for proper operation. Should the D-2® governor not meet the elements of the operational tests noted in this document, further investigation and service of the governor may be required.

SERVICE TESTS

OPERATING TESTS

Start the vehicle engine and build up air pressure in the air brake system and check the pressure registered by a dash or test gauge at the time the governor cuts-out, stopping the compression of air by the compressor. The cut-out pressure should be in accordance with the pressure setting of the piece number being used. (Common cut-out pressures are between 105-125 psi.) With the engine still running, make a series of brake applications to reduce the air pressure and observe at what pressure the governor cuts-in the compressor. As in the case of the cut-out pressure, the cut-in pressure should be in accordance with the pressure setting of the piece number being used. (Common cut-in pressures are between 90-105 psi.)

LEAKAGE TEST

Leakage tests on the D-2® governor should be made in both cut-in and cut-out positions.

CUT-IN POSITION

Apply soap solution around the cover and to the exhaust port. Slight bubble leakage permitted. Excessive leakage indicates a faulty inlet valve or lower piston o-ring.

CUT-OUT POSITION

Apply soap solution around the cover and to the exhaust port. Slight bubble leakage permitted. Excessive leakage indicates a faulty exhaust valve seat, exhaust stem o-ring, or o-ring at the top of the piston.

If the governor does not function as described or leakage is excessive, it is recommended that it be replaced with a new or remanufactured unit, or repaired with genuine Bendix parts available at authorized Bendix parts outlets.

GENERAL SAFETY GUIDELINES WARNING! PLEASE READ AND FOLLOW

THESE INSTRUCTIONS TO A VOID PERSONAL INJURY OR DEATH:

When working on or around a vehicle, the following general precautions should be observed at all times.

1. Park the vehicle on a level surface, apply the parking brakes, and always block the wheels. Always wear safety glasses.

+ 2 hidden pages