About Us    Contact Us

Pressure relief valve opens on air compressor

Published Categorized as Air Compressor Valves, Uncategorized No Comments on Pressure relief valve opens on air compressor

PRV pops every 1/2 second until compressor turns off.

by Michael

Hello, my tank which max at 175 psi, will run and shut off normally, except PRV at the start of intercooler pops air every 1/2 second or so until the compressor hits 175 psi.

The PRV is new with correct spec spring.

First I thought it was the oil that ran a little low, but that wasn’t the problem.

Please help.

Thank you very much!


Mike, is your air compressor a two stage one, with the second cylinder increasing the pressure of the air going into the tank?

That being the case, you may want to check out the intake valve on the secondary pump cylinder.

Pop off valve on a Wayne Mod# 6378-SH

by Al McDaniel
(Newark, Oh)

Hi Bill,
I have a Wayne Mod# 6378-SH air compressor; it is a V-Twin.

The low side relief valve on one of the compressors pops off when the lines pressure gets to about 120psi.

I figured I had to have a valve hanging open or closed so I started removing the manifolds’ looking for a stuck or malfunctioning valve. All valves were free and could not see any problems. I reassembled the unit and still had the same problem.

I replaced the check valve knowing it was a long long shot but said what the heck.

I can’t think of any thing other than a malfunctioning Exhaust valve for the low pressure side that would cause the valve to pop off.
Any ideas or suggestions are deeply appreciated.

Al McDaniel
Al, my goodness, aren’t these 1950’s vintage air compressors you have?

One thing you didn’t try is to replace the PRV. It is possible, remotely so, but still possible that it’s failing and letting go early.

Still, if this is a 2-stage compressor, and I believe it is, and the low pressure cylinder feed line to the higher pressure cylinder has it’s PRV let go, and it’s not the PRV itself, I’d still think it was the valve on the high pressure cylinder reacting to pressure some how.

Anyone else?

I also found this for you, for parts:


Pressure – prv opens

by David

My compressor builds up pressure fine but when it gets to the normal cut off the pvr opens n releases the air down to about 40 psi so it keeps running the motor could it be the pressure switch? Thanks
Hi David. If the pressure switch cut out is, for example, 120 PSI, then the air compressor should shut off at that pressure.

If the pressure switch fails with current passing it to the motor, the compressor will continue to run and pump pressure into the tank, until the tank pressure reaches the PRV release pressure point, and the PRV opens to vent overpressure.

You say “gets to the normal cut off the pvr opens n releases the air” then if the PRV is opening at the pressure switch normal cut out pressure setting, then it is the PRV that is suspect, not the pressure switch.

Airmate 12/25.0 OL230 – safety valve trips

by Jan Kent

safety valve trips before compressor gets to stop at max pressure.
If I cut the power before the safety trips and then put it back on,the pumps stays off while I use the tool (nail gun or stapler) and when the pressure drops by around 30psi the compressor comes back on. So as long as I substitute for the max pressure switch I can work. It used to work and I don’t know if I have done something that has made the safety operate too low or if I have somehow set the Max switch too high.
Jan, if by the safety trip you mean the PRV lets go to bleed off excessive pressure, then it is either that you have adjusted the compressor cut out setting to a set point higher than the PRV release pressure, or the PRV is failing.

At what pressure is the PRV letting go? Please advise.

Comment? Please add it here along with photos to help others help you with your compressor and equipment problem!

By Bill Wade

About Air Compressors has been helping folks with their Air Compressor Problems since 2002 online. We're a community of DIY and Compressed Air professionals who are keen to support everyone across the globe with their air compressor issues and troubleshooting. Whether you're trying to identify an old air compressor, or troubleshoot an error code on a sophisticated new industrial air compressor - the community at About-Air-Compressors.com is here to help you

Notify of
Inline Feedbacks
View all comments