HoserRacing
HoserRacing HalfDork
11/9/20 8:24 a.m.

I've got an older Campbell Hausfield that was my first serious shop purchase years ago.  It's served me well, until a couple of weeks ago.  When it shuts off, it's leaking air from the valve that's supposed to turn it on when the pressure drops.  

Picture of switch

The brass fitting should tell the switch to turn on the compressor when the pressure drops if I understand the set-up correctly.  But when the switch is in the off position, air is leaking out from the brass trigger assembly.  I bought a new Square D unit, replaced it, and I'm still having an issue.  Does this mean that I have a problem elsewhere on my compressor?  I appreciate any knowledge y'all can share.  Thanks!

 

David

NOT A TA
NOT A TA SuperDork
11/9/20 9:49 a.m.

In reply to HoserRacing :

  " When it shuts off, it's leaking air from the valve that's supposed to turn it on when the pressure drops."

    "But when the switch is in the off position, air is leaking out from the brass trigger assembly."

Sounds like it's leaking all the time? But you only can hear it when the motor shuts off.

I'd get some (thick) soapy water & an acid brush and check your pipe connections and the pipe to see if you get some bubbles where there's a leak. The likelihood of both the original and your new one having an internal leak is pretty slim so it's probably fittings leaking or a little crack in the pipe. Did you clean pipe threads and fittings and use Teflon tape or paste when reassembling?

HoserRacing
HoserRacing HalfDork
11/9/20 9:55 a.m.

I'll try shutting it off by turning off the power to it instead of flipping the switch and see if it still leaks, hadn't thought about that.  It's a flared line going in, and I made sure it was clean before hooking it up.  Where this line comes over from the compressor head, everything in sight seems ok. I'm not sure if something inside the compressor head has gone south and is letting air blow by, or what my issue may be.  

I'll try the soapy water, see if I can determine whether it's in the fitting or pipe.  I didn't use any paste or tape since it was a flare fitting.  

NOT A TA
NOT A TA SuperDork
11/9/20 10:22 a.m.

Ya, flare doesn't require Teflon. Couldn't tell whether tapered or flare in pic.

It will still leak with the power off as the pressure switch isn't affected by whether there's power or not.

HoserRacing
HoserRacing HalfDork
11/9/20 10:25 a.m.

Actually, the switch (best that I can determine from looking at it) has a plunger that is activated by the air pressure, and causes the rocker to turn the switch on and off.  If I turn the switch to the off position, it's moving the plunger, and the air is coming out.  I guess I should really video it because I'm terrible at giving verbal descriptions.  

bentwrench
bentwrench SuperDork
11/9/20 11:00 a.m.

Big compressors have an "unloader" that dumps cylinder pressure so the compressor can restart easily.

The unloader will continue to bleed off air if the cylinder check valves are leaking.

NOT A TA
NOT A TA SuperDork
11/9/20 11:07 a.m.

My mistake, I should have said "even if the compressor isn't plugged in the leak will be the same" because electricity doesn't change how the switch itself operates.

The air pressure turns the switch off against the adjustable spring pressure.

HoserRacing
HoserRacing HalfDork
11/9/20 11:13 a.m.
bentwrench said:

Big compressors have an "unloader" that dumps cylinder pressure so the compressor can restart easily.

The unloader will continue to bleed off air if the cylinder check valves are leaking.

Ok, this may be what's happening. I'm used to when it shuts off having that momentary "pssshhhh" that then stops. I've never dug into a compressor before, any advice on checking the check valves?

NOT A TA
NOT A TA SuperDork
11/9/20 11:21 a.m.

In reply to HoserRacing :

The bigger ones have a valve on the cylinder head with a ring like a cheap key ring you can pull to activate the valve.

HoserRacing
HoserRacing HalfDork
11/10/20 6:36 p.m.

Ok, here is a video of me turning the compressor on with the switch, then turning it off with the switch.  When I turn it off, you can hear the air leak from the valve.  

Compressor leaking when off

Here is the video with the power off, there is no leak when the switch is in the on position, just in the off position.  It never leaked that before with the old switch until it went bad, so not sure if something else has failed and this is just the evidence.  

Moving the switch to demonstrate leak

I also noticed that the compressor was acting a little weird when I was running it.  Not sure if the compressor head might be going out?  I just put a new wire to the compressor, put it on a plug so that I can unplug it and use that outlet for other things as well (just had a buddy bring his camper to stay while we went to a nearby race, used it to run a line out to his camper).

 

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