There's air blowing straight through the air dryer.

I replaced the purge valve, and went ahead and put a new filter on too. I turned down the governor cut-off to 90 psi and it still blew air through (I turned it back up).

System drops and rebuilds on a 33 second interval when it's at its worst. Sometimes it drops and holds at about 100 psi for a little while before rebuilding again. Only the primary air drops; secondary air is stable.

I'm afraid my compressor is going to burn up. What could be causing this problem? Is there another valve somewhere between the air compressor and the air-dryer purge valve that might be bad?

As a last resort I'll go to a shop, but these days I fancy doing the repairs myself.

Primary air shouldn't be dropping, after fixing the purge issue, you also have a check valve to replace between the wet tank and the primary.

Something is wrong with the purge valve. Did you get the signal line from the governor properly re-attached to the purge port?

Maybe a seal or o-ring out of place or didn't get in there right on the re-install? Check the filter re-install too, something between the two in conflict?

Temporarily, to get operational until you get home/get some inexpensive help, you can bypass the air drier by linking the input and output hoses together with some hardware. Drain the wet tank daily while in a bypassed configuration!

Does this always leak out the purge valve? While the compressor is building air the purge valve exhaust is closed. Once the compressor stops making air, the purge valve opens and stays that way until the compressor starts making air again (this is where that PRI air would leak past the check valve and out the purge). What air compressor? What dryer? Truck build?

I had a similar problem on mine truck and even replaced the entire air dryer and it didn't help. on top of air blowing through the end of the drier there was also this crazy whistling sound made by this air (because of the high pressure and narrow opening). people were literally turning their heads when i was pulling into truck stops there was also a leak in a couplings on the wet and dry tank and I had those fixed (where the air hose connects to the tank). This helped somewhat but really cured this problem was draining the wet tank every morning in warm weather and every night in cold weather. Before I used to drain the wet tank only a couple of times a week, but after I switched to doing it daily, the dryer stopped whistling Try spraying windshield wash on tank couplings with the engine working - you might have a leak there. And try draining the wet tank every day FULLY, until no air is left in it.

take a look at this. this may help http://www.bendixvrc.com/itemDisplay...ocumentID=2568

Ooops. I forgot about this thread. I replaced the air dryer body and the problem was solved. Still not sure what was going on to make air blow straight through like that.

Its nothing but the odstacles that comes in its path ....not to worry about it... just have a clean look inside the air vent and thats all and yes try this when the dryer is shut off...

Just how do you "shut off" the dryer?

I'm duessing he is reffering to shutting off the motor, hence no air is being supplied to the system but I might be wrong. To replace the filter on my AD-9 was $59.00 and seeing it had a good 800k miles on it, I just spent the $300 and replaced the whole unit. SOmetimes it's easier to replace than rebuild.

You didn't trade it in for core value? Sale price in the fall up here is anywhere give or take $165 with trade in for a fresh re-build. Lots of fleets swap the whole thing, cheaper on the paid time to the mechanic than a proper pm on the drier.