C4500 & C5500 Compressor Replacement


Tools Needed:
18mm & 12mm Open End Wrench Torx
Philips Screw Driver

If your truck came equiped with a factory exhaust brake or air ride seats and they stopped working, there is a good chance your compressor has failed.  But before you just replace it, you should check a few other areas first.  Start by draining your tank(s) and checking the compressor for power with a multi-meter with the key in position II/run.  This is accomplished by disconnecting and checking the voltage at the compressor wiring harness closest to the actual compressor (highlighted in Figure 2).  If it shows12v than more than likely your compressor is bad.  If you do not have 12v your problem is elsewhere, perhaps in the low pressure switch or the relay.

Once you have confirmed the compressor is bad start removal of it by first assuring the tanks are drained.  Locate the compressor assembly under the drive door.  Now disconnect the compressors air-line from the tank.  Fittings vary but in most cases you need a 12mm open ended wrench.

Compressor for air ride seats and exhaust brake
Figure 1

Un-plug the assembly harness highlighted in Figure 1 above.  This is done by depressing the retainer and gently pulling it apart.  Now remove the two bolts circled above.  They are captive on a bracket behind the frame rail so there is no chance of losing anything.  Once both bolts are removed the entire compressor assembly will lift out as show below.

Compressor out of the truck
Figure 2
Now to replace the pump you need to remove the two torx circled above.  Next remove the harness (the one you used to check the voltage) and finally a single philips screw on the back side of the compressor.  If you are installing another OEM pump re-assemble everything in reverse order checking all the fittings for leaks with soapy water.  The OEM compressor has a history of  failing prematurely.  It is for this reason we reccomend replacing it with an aftermarket pump such as a Viair compressor.  Check the review section for reviews on the Viair unit, or the modifications section for "how to" instructions on upgrading to an aftermarket pump.

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