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Forum topic by MNWOODWORKER posted 03-29-2009 06:34 AM 4957 views 0 times favorited 15 replies Add to Favorites Watch
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MNWOODWORKER

105 posts in 3053 days


03-29-2009 06:34 AM

Topic tags/keywords: question

I am having troubles with my air compressor. When it pumps up it will reach 130psi just like it should and then it kicks out but then all the air will leak back out the pressure switch, then it will pump back up and do it all over again. I have even replaced the pressure switch thinking it will solve it, but same thing with the new one. It is a belt drive unit that is about 10 yrs old. Any ideas would be great.
Thanks again,
n.e.


15 replies so far

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TopamaxSurvivor

17677 posts in 3144 days


#1 posted 03-29-2009 07:42 AM

Are you absoutely sure that is where the leak is? If you are, sounds like you got a bad swith to replace a bad switch.

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

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MNWOODWORKER

105 posts in 3053 days


#2 posted 03-29-2009 08:10 AM

Yeah I am sure. I took the cover off the switch and held down on the lever that that is letting the air out and it stops, leave go of it and it leaks again. It is no little leak either, it puts out more air than my blow gun! While it is pumping up it does not leak, but when the switch kicks out it opens the lever and leaks. Still think I just got another bad switch?? Thanks for your time.
Nate

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TopamaxSurvivor

17677 posts in 3144 days


#3 posted 03-29-2009 08:27 AM

I’ve work on quite a few pressure switches in the last 40 yrs and I don’t remember any lettting any air out. Sounds like there may be a built in over pressure relief or something of that nature you are dealing with. The manufacturers are always coming up with cheaper ways to combine parts, ect. Is there a pressure relief device on the compressor else where?

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

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marcb

768 posts in 3141 days


#4 posted 03-29-2009 04:04 PM

There is a valve on the compressor tank that has a small tube that goes to the pressure switch. On mine its just a brass circle with a spring. Sounds like this is stuck open. It opens when the head kicks so that it isn’t fighting full pressure while pumping.

I took mine apart and cleaned up the valve body and it works fine now. The other side of the problem is if it gets stuck closed you’ll trip your breaker when starting with pressure in the tank.

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TopamaxSurvivor

17677 posts in 3144 days


#5 posted 03-29-2009 10:42 PM

Unloader valves are quite common on industrial compressors. How big or what kind are the compressors you guys are talking about?

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

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MNWOODWORKER

105 posts in 3053 days


#6 posted 03-29-2009 11:00 PM

It is a 27 gallon coleman powermate (same thing as a sanborn) 5hp belt drive unit. I took a pic of the pressure switch, now just trying to figure out how to get it on here, I am not to good with this stuff. The pressure switch is also the on-off switch and it gets attached to the manifold that has the gauges, blow off valve, and the outlet. Inside the pressure switch it has the wires that go to the motor and to the outlet, and the switch itself that is tripping after it pumps up all the way and then letting the air out. It does not leak until it reaches 130 psi and kicks out.

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MNWOODWORKER

105 posts in 3053 days


#7 posted 03-29-2009 11:03 PM

marcb, thanks for the advice, I had that problem in the past and tried it already, I couldn’t get that lucky.
ne

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TopamaxSurvivor

17677 posts in 3144 days


#8 posted 03-29-2009 11:43 PM

That switch should not be leaking to the atmosphere until the comnpressor restarts in an endless cycle. If cleaning it doesn;t work as marcb suggested, take it back for a replacement. You can probalby adjust it to a lower setting if you need to get by until you can replace it. There should be 2 adjustments; one for the maximum pressure and another for the differential that tells it when to come back on. I’m not familiar with this particular switch, so there is a possibility youi might just adjust the leak to a lower setting. Good luck.

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

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CharleyL

197 posts in 2832 days


#9 posted 03-30-2009 12:19 AM

There is a check valve in the fitting where the air line from the compressor enters the tank. It is likely leaking and letting the tank air back into the line from the compressor. The bleeder valve in the switch is designed to let the air out of this line when the compressor shuts off so that the compressor can start without a load, but in this case it continues to let the air out that is leaking past the check valve and the tank pressure drops, causing the compressor to start again. Sometimes these check valves only need to be removed and cleaned, but it may be necessary to replace it. To service it disconnect the power and then remove ALL of the air from the tank. Then unscrew the fittings where the air line from the compressor enters the tank. The bottom most fitting is the check valve. It likely is also where the small bleeder line connects (to the side) that runs to the pressure switch. Once you get it out, you will see the small metal diaphram in the bottom that is the actual valve. It is spring loaded up against the air entrance port. The air pushes it down to enter the tank (possibly through side holes). Either there is dirt between this air port and the diaphram or the seat of the port is corroded. If the latter, you need a new one. Fortunately they are a fairly standard design and any compressor service center should be able to supply one. It may not look exactly the same, but if the fittings are the same size and it has the bleeder line connection it will work. They are usually in the $10-15 range.

Charley

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TopamaxSurvivor

17677 posts in 3144 days


#10 posted 03-30-2009 12:32 AM

I’ll put my two bits on CharleyL’s diagnosis. That makes sense as to why the switch is leaking when it shuts off. If that check valve is out, it will never hold air at any pressure :-))

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

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MNWOODWORKER

105 posts in 3053 days


#11 posted 03-30-2009 05:55 AM

Thanks alot everyone. I will take a look at it tomorrow. I will let you know what I come up with.
Nate

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sIKE

1271 posts in 3222 days


#12 posted 03-30-2009 06:56 PM

Take a spray bottle add 95% water and 5% dish soap. Spray it where you think you hear the leak. It will bubble up and you will then at least know where to start.

About 25 years ago I was staying at my Uncles over the summer and one of the gas meters in the easement was leaking and the utility guy used a sprayer like this to find the leak. My curiosity go the better of me (there was a natural gas leak) and I had to ask him what he was using. The above solution was the very surprising answer to my youthful mind.

-- //FC - Round Rock, TX - "Experience is what you get just after you need it"

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MNWOODWORKER

105 posts in 3053 days


#13 posted 04-01-2009 07:30 AM

Thanks alot everyone. I took the manifold off and took it all apart and cleaned everything, luckly I have a small stacker unit for when I do any jobsite work, blew out all the passages, still no luck. Then out of desperation I took the ball and spring up to Napa and found a match for the ball (it looked fine but felt harder than I thought it should be) and got a spring with a little more force, not much but a little. That seemed to make the difference. I don’t know if the ball was too hard to actually seal or if the spring was just getting weak. It doesn’t matter I HAVE AIR AGAIN!!! Thanks so much for everyones input and help. The other thing is that I put the original switch back on and it works fine, I guess I have an extra now.
Nate

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TopamaxSurvivor

17677 posts in 3144 days


#14 posted 04-01-2009 06:23 PM

Does your compressor still bleed off when it stops at 130#s? If it doesn’t your motor is starting against a full head of pressure. That will dramatically increase the starting spike current.

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

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MNWOODWORKER

105 posts in 3053 days


#15 posted 04-02-2009 07:10 AM

Yes it bleeds off for about 10 seconds or so after it kicks out. After use, the pressure drops to around 85psi then it will recycle. It seems to be working as good as new. Thanks again for all your time and letting me pick your brain. Take care.
Nate

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