Air Compressor Will Not Build Air Pressure - keywords brake compressor haydex hydraulic

This PI is being superseded to update recommendations / instructions. Please discard PIT4145.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Some 2007 medium duty models with 7.8L Isuzu Diesel Engines and air brakes or hydraulic brakes with RPO KK3 equipped with Haldex Air Compressors built between SOP and September 20, 2006 may not be able to build air pressure. Haldex has advised that some air compressors may have been improperly assembled with loose or missing internal fasteners that would stop the compressor from building air pressure. The assembly plant has contained all units in their inventory and the supplier has people on site to rework the air compressors.

MODELS WITH AIR BRAKES:

If the Haldex air compressor will not build air pressure, the air brakes will remain applied and the truck will not move. The air gauge in the dash will indicate no air pressure and the low air pressure alarm will sound. If the truck is being driven, the air brake system will operate normally but will not build air pressure after a brake application. The pressure will drop to the point where the low air pressure alarm will sound and the driver will have to move the vehicle to a safe location. If the driver continues to drive the truck, the emergency air brake system will eventually automatically apply and the truck will not move.

MODELS WITH HYDRAULIC BRAKES AND RPO KK3:

If the Haldex auxiliary air compressor RPO KK3 will not build air pressure, there will be no auxiliary air supply to operate options such as air suspension, air seat, air horn or other auxiliary air operated systems. The hydraulic brake system would not be affected.

All trucks with Haldex air compressors built beginning September 21, 2006 and forward will have properly assembled air compressors. GM Service Parts stock of Haldex air compressors have been returned to the supplier and new qualified stock will be identified with a blue or white paint dot on one of the air compressor cylinder head bolts.

If a 2007 truck in service has a Haldex air compressor that will not build air pressure, a replacement compressor P/N 15284284 should be ordered from GM Service Parts and the removed compressor will be returned to Haldex. Follow instructions in SI for service replacement of the air compressor assembly.

Note: Always check the air dryer and governor assembly for proper operation after replacing the air compressor. It may be possible for loose air compressor plate screws to be drawn into the compressor air discharge, blown down into the air dryer and get jammed inside the dryer or the dryer purge valve.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.