Compressor help

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Forum topic by Craftsman on the lake posted 02-03-2009 11:00 PM 1126 views 0 times favorited 7 replies Add to Favorites Watch
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Craftsman on the lake

2848 posts in 3679 days

02-03-2009 11:00 PM

Topic tags/keywords: compressor air tools repair question

Calling all compressor repairmen!

I have a large compressor I’ve been given. I use air tools but with this baby I’d be able to use some that require lots of volume. Don’t know much about it but it runs nicely is one of those stationary upright ones about 5 ft tall with a two piston compressor, large motor. I’d look up specs but it’s very cold out and I don’t want to go out to the garage with a flashlight to find info on it.

It’s 220 volts and I have it hooked up with two 30 amp bus fuses in a switchbox which is standard. When I start it it runs well, comes up to pressure but won’t stop at 120 lbs. I’ve taken the cover off the switch box and tried to adjust the screws to see if I can change the stop/start pressure but it has no effect. If I let it get to high it will blow the fuses so I have to cut it off manually before that happens. The unit has had little use, maybe a dozen hours. So, should I replace the switch? or could it be something else.

Thanks in advance.

-- The smell of wood, coffee in the cup, the wife let's me do my thing, the lake is peaceful.

7 replies so far

View PurpLev's profile


8548 posts in 3890 days

#1 posted 02-03-2009 11:36 PM

how cold was it when you fired it up? I noticed you’re in maine, and recently temperatures around here have been pretty drastically low… I’ve had a similar experience with my compressor 2 weeks ago, where it just wouldn’t stop filling the tank, I had to manually turn it off…

I think it might be the cold temperature that is messing up the dials/compression gauge, and doesn’t shut off the compressor when it hits a limit PSI.

now that it’s ‘warmer’… (only 30f) it works fine…. it was acting up when it was ~10f I believe

-- ㊍ When in doubt - There is no doubt - Go the safer route.

View Woodchuck1957's profile


944 posts in 4005 days

#2 posted 02-03-2009 11:46 PM

The shutoff may be set for 125 psi or 135 psi, hard to say, try to get a manual for it, then you will know.

View hairy's profile


2783 posts in 3773 days

#3 posted 02-04-2009 12:14 AM

Make sure you bleed off all the air in the tank before you pull that switch off. Maybe spray in some wd-40 and put it back in,sometimes they stick. I have to hit mine to get it start back up.

-- My reality check bounced...

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Craftsman on the lake

2848 posts in 3679 days

#4 posted 02-04-2009 12:40 AM

I’ve had it for a few months so it was tried in warm weather. I just had other things to do so left it till this spring. I just thought I’d pick peoples brains now.

I didn’t think of lubricating the switch. I’ll try that.

-- The smell of wood, coffee in the cup, the wife let's me do my thing, the lake is peaceful.

View NY_Rocking_Chairs's profile


527 posts in 3838 days

#5 posted 02-04-2009 01:46 AM

It might have an emergency bleed valve too. Mine has one and I think it is set for around 150 or 160 PSI. Of course if the switch stuck it wouldn’t prevent the pump from running 24/7 but it would prevent it from blowing up.

-- Rich, anybody want a peanut?

View bendisplays's profile


40 posts in 3642 days

#6 posted 02-05-2009 10:41 PM


The pressure switch may actuall be bad. Replacing it may be necessary and depending on the compressor it can be expensive.

Now before I go too far lets eliminate a few things.

Have you just manually started the compressor?

The reason that I am asking this is: If you are just starting the compressor with a disconnect switch and it does not start from the actually pressure switch activating on low pressure, then you may have a clogged passage between the pressure switch and the compressor tank.

Now another problem is that the pressure switch may not be connected. (I am not infering this is the case but I do want to bring it up so it can be fixed if this is the case) I have bought and wired many larger compressors. Often when I have bought a used compressor, the pressure switch is not wired to a motor conntactor (A large relay). In this case, if you would turn the compressor on it would not stop or conversely it would not restart once the compressor’s air pressure is low.

I want to note that many single phase compressors are not wired through a contactor. It is best to trace the wire from the pressure switch and see if it is hooked up so it is inline with the power coming in. You might be surprised and this would be an easy fix.

If the pressure switch is not contacting, there can be a couple of problems with the most common being the contacts are corroded. You can fix this by getting fine emery cloth sand paper and sanding the contacts in the pressure switch.

If all else fails buy a new pressure switch. If you have any questions about wiring or function of your compressor please let me know.



View Craftsman on the lake's profile

Craftsman on the lake

2848 posts in 3679 days

#7 posted 02-05-2009 10:45 PM

thanks bendisplays… all good things to look for. I’m keeping a running list of things to look for once the temp goes above zero.

At that point I may contact you to pick your brain. So, don’t go anywhere!

-- The smell of wood, coffee in the cup, the wife let's me do my thing, the lake is peaceful.

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