It all started with air leaking from the unloader, at the pressure switch. I purchased a new pressure switch. A new unloader assembly was included. I replaced the old switch & installed the new unloader.


Husky-Pro- 30 gallon air compressor.


I started the compressor & let the tank fill. When the tank was full, the pressure switch would not trip (shut off) as it’s supposed to. Instead, the PVR opened. However no leak was detected at any point in the unloader assembly.

I disassembled the check valve assembly & found a bad check valve.

So, I replaced the compressor’s check valve. Again, after filling the tank, the PVR opened again. And no leak detected.

I’m about ready to pull my hair out. Can anyone shed some light on this?

Sorry you had to buy a new pressure switch.

Compressed air blowing out the unloader valve when the compressor is running usually means the unloader valve has failed. If air is blowing out the unloader valve when the air compressor has stopped, then it is most often a failed tank check valve that is the cause of this.

Air blowing out of the PRV at a lower pressure than the normal cut off pressure of the compressor typically means the PRV has failed and needs replacement.

If the PRV is OK, then as to your new pressure switch, I suspect either the switch is installed incorrectly and isn’t cutting power when it should, or it has a too high cut out pressure setting, or it has failed.

There isn’t enough information about the pressures in the tank when the problem occurs to be specific.


Got it running right!
by: Anonymous

Hello Bill.

Thank you for posting my dilemma.

Well, it turns out that after replacing the pressure switch, the check valve, & the unloader valve, I found that the PRV was bad. (Actually, all of the parts needed replacing.) So, I found a place that carries that part, spent another $12.00, and wah-lah! Success!

I forgot to mention that the tank max pressure is rated 175 psi. If you looked at the picture, you’ll see two gauges. The gauge on the left (the “out” pressure) was set too high. I adjusted down to about 75 psi. I turned it on, and it ran like a champ, shutting off by itself, like it’s supposed to.

Hopefully, this posting can save someone the trouble of having to figure out the solution to the same problem I was having.

Thanks again Bill!


You are welcome. Glad you got your compressor running properly.