If the air pressure is being governed at either a higher or lower pressure than the equipment manufacturer’s
specification, connect a regulated shop air pressure line to the air compressor governor air signal port.
NOTE: Be positive the gauge is accurate and the supply lines and fittings are in good condition before performing
any air pressure checks. Use a master gauge of known accuracy to check the air pressure gauge.
NOTE: When performing the test, be sure the air system pressure does not exceed the manufacturer’s maximum
• Inspect the governor control lines for restrictions.
• Drain the air system and install a gauge of known accuracy onto the unloader port of the air governor.
• Start the engine and apply the brakes to initiate air compressor pumping. Note the governor cut-out pressure (pressure at which the compressor stops pumping).
• Apply the brakes until the compressor starts to pump.
Note the cut-in pressure.
NOTE: Zero pressure in the governor unloader line will allow the compressor to start pumping.
• Apply the brakes until the compressor starts to pump. Note the time it takes for the governor unloader port to
go from system pressure to 0 kPa [0 psi]. The cycle should take less than 2 seconds.
• Repeat steps three through five for a total of 3 runs.