In article 1133380318.857778.212840
@z14g2000cwz.googlegroups.com, says...
Hi people,

Went to the shop this morning to find the air compressor (Campbell
Hausfield 6hp, 125psi) runnning and a big air leak from somewhere.

Pressure was at 40lbs and I could feel a lot of air escaping around the
control switch. I could not see exactly from where. I shut it down and
after a few seconds more air rushing out, something clicked and the air
leak stopped.

After some more looking around I found a pressure relief valve under
the switch so I assume this was stuck open. I tried it an sure enough
air escaped again but it closed itself when I let go the keyring just
as I expected.

I started the thing back up and it went to 120lbs and shut down
normally. I tried the pressure relief and it stays out with air
escaping until pushed back in.

Can someone who has one of these air compressors check their pressure
relief valve when the tank is at full pressure and tell me if the thing
spring returns or stays out. I may need a new relief valve or at least
clean out this one. I thought I'd ask before commiting to that though.

The safety relief should not reseat itself until the
pressure drops well below its setpoint. I wouldn't consider
the compressor safe to operate until you figure out what
caused the overpressure condition that opened the relief.
The most likely culprit is the pressure switch.

Ned Simmons