Operational Test Procedure
sd mm 42.03.001
Important: Review the warranty policy before performing any intrusive maintenance procedures. An extended warranty may be voided if intrusive maintenance is performed during this period.
Every 12 months, 100,000 miles (160 900 km), or 3600 operating hours, perform the operational test below.
- Start the vehicle engine, build air pressure in the 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. Cut-out pressure should be in accordance with the pressure setting of the piece number being used. Common cut-out pressures are 125 to 135 psi (862 to 931 kPa). 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 cut-out pressure, cut-in pressure should be in accordance with the pressure setting of the piece number being used. Common cut-in pressure is 105 psi (724 kPa).
- Never condemn or adjust the governor pressure settings
unless they're checked with an accurate test gauge or a dash gauge
that's registering accurately. If the pressure settings of the D-2
governor are inaccurate or it's necessary that they be changed, the
adjustment procedure follows.
- Remove the top cover from the governor.
- Loosen the adjusting screw locknut.
- To raise the pressure setting, turn the adjusting screw counterclockwise; to lower the setting, turn the screw clockwise. Be careful not to overadjust. Each 1/4 turn of the adjusting screw raises or lowers the pressure setting approximately 4 psi (28 kPa).
- When proper adjustment is obtained, tighten the adjusting screw locknut, and install the top cover. The pressure range between cut-in and cut-out is not adjustable.
Note: If the governor cover is marked nonadjustable, and the adjusting stem has been sheared off, this is a non-serviceable governor and it must be replaced with a new or remanufactured unit.
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