T680 air compressor

You have an airleak somewhere. Get soapy water and spray everything down. Including transmission lines and trailer lines if it's the same trailer.

 

What is seems to be coming on a lot? How often is it cycling? Time it. At idle with no brake applied cycle should be 2-3 minutes. Were the brakes released when the truck was sitting still and you checked for leaks? Possible compressor unloader malfunction. Did you check the air dryer?

 

If the compressor is cycling on/off more often than it should with the truck just parked bobtail and idling and you don't notice the pressure dropping off on the gauges, most likely a leak somewhere between the compressor and the wet tank or in the governor/unloader circuit.

 

Do you mean it’s purging frequently? Trace the signal line from the air governor to the compressor unloading valve… you probably have a break in it somewhere.