Why does my compressor keeping kicking out?

Better now than cold as Billy he,ll miles from a shop or middle of no where..
Orrrrrr at a shop that will hose you .

 

Hi Dave,
Sounds like you have an air leak in the unloader circuit for the compressor and air dryer. When pressure in the system reaches the set pressure of the air governor, the governor sends air to the compressor and dryer. This signal of air does two things; it operates a valve in the compressor and stops it from building air, and opens a purge valve in the air dryer. Any leak in this system will result in a loss of pressure in the unloader circuit and the governor will reset and the system will begin building air again. The reason you don't see this on the gauges in your dash is that the governor gets air from the wet tank. This tank is after the dryer but before the primary and secondary tanks (dash gauges). A sketch would make this very clear.

A quick way to troubleshoot and maybe get lucky is to run the engine until the compressor unloads and you hear the air dryer discharge. Turn off the engine and then go to the engine bay and listen for any leaks. Listen at the purge valve for the dryer and any of the hoses coming off the air governor. Internal air leaks in the compressor are typically not external so you're not likely to hear anything there.

It's important to know that this unloader circuit will only be charged with air when pressure in the wet tank is above 90 psi, and that's only after the governor has unloaded (reached 120 psi on build up). Again, pressure in the wet tank is not reported on the gauges so you can ignore them. The "minute or two" between purge cycles is the period of time when air will be present and possibly leaking.

hope this helps,

 

Air leaks at the compressor may be difficult to hear if they are internal. That's what I meant to say.

 

The cartridge too...?

Pull the intake air supply line off the compressor run truck check to see if air is leaking back out the intake.....

 

I fought a problem like this when first switched from the AD-9 Drier. Since then, we switched the push in connectors at the drier and the Compressor unloader to the good old brass ferrules type fittings. We also switched away from the $20 TRP spin on cartridge and started buying Wabco meritor cartridges (With the oil wicking layer pt# R950068A) for about $80 and change them every fall. This has cleaned up most of them from acting up.

I have had to replace a two entire units since I made these changes, both where on trucks that I fought air leaks. The two little plastic check valves inside wore the aluminum housing out crooked and they would seal anymore.

The new style driers (I’ve seen about 3 different ones) seem to be very prone to act up anytime there is any leak between the compressor inlet and drier outlet, (both the control and supply sides and inside the compressor head/ unloader valve).

So if the flow out of the drier is pulsing it’s a weak control circuit (sticking comp unloader, leaking drier unloader or leaking control line) if it’s a steady flow it’s a bad check valve (either internal or the outlet)

 

Had that problem once. Was a push to connect fitting leaking on the small sensor line between governor and wet tank.