 Compressor Help (OT)
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Joined: Jan 2005
Posts: 5,537
Check Pants
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OP
Check Pants
Joined: Jan 2005
Posts: 5,537 |
Folks: I have an issue with my relatively new, Harbor Freight upright garage compressor. The unit is about a year old, but only seen light use. Last month, it wouldn't start and sounded like it was straining, so I immediately shut it off. I pulled the motor cover and found two motor screws had backed out, into the cooling fan blade. This was the straining sound I heard. I put the two screws back in place, checked the others and fired it up. The unit started right up and filled the canister to 125 lbs of air, as normal. As the motor shut down, a small brass bleeder type valve in the switch popped up, releasing all the air. At 90 lbs, it started running again, but it constantly releases all the air. I fiddled around with the two adjustment screws, one of which is a plastic screw in the plastic switch housing. I screwed it down too tight, breaking the end of the plastic housing. I ordered a replacment switch on Ebay, and it was identical to the OEM switch (Harbor Freight was back ordered on the switch for several months). I put the new switch in, and the same thing happens, as soon as it hits 125 lbs, that bleeder valve releases all the air. Here's a picture of the top of the switch, showing the two screws:  Here's that bleeder valve built-in to the switch housing. It's directly under that brass union nut:  Does anyone know what is causing this bleeder valve to release? It never did this before and would hold air for several weeks.
Al
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Re: Compressor Help (OT)
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Joined: Feb 2006
Posts: 3,099
Loquacious
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Loquacious
Joined: Feb 2006
Posts: 3,099 |
I think what you're calling a bleeder valve is an over-pressure relief valve that has failed, and needs replacement.
Just a guess,
Uncle Charlie
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Re: Compressor Help (OT)
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Joined: Apr 2007
Posts: 3,063 Likes: 8
Loquacious
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Loquacious
Joined: Apr 2007
Posts: 3,063 Likes: 8 |
You don't normally run your compressor above 100psi. This is adjustable at the switch. If I remember correctly, one screw is for the low pressure setting (turn on) and the other is your max setting (shut down). Your compressor high setting should shut the compressor down at around 100 psi and kick in where you want it, typically at around 80 to 90 psi.
What is bleeding down is the safety bypass or over-pressure relief valve designed to do what it is doing, prevent the tank from overpressurizing and blowing up.
You also have a pressure regulator which restricts outpressure from the nozzle.
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Re: Compressor Help (OT)
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Joined: Jan 2005
Posts: 6,821
Bar Shake
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Bar Shake
Joined: Jan 2005
Posts: 6,821 |
I keep mine set at 155psi, kicks on at 130. It's a Coleman and the switch area doesn't look like yours.
Mine is rated at 155psi max. Check your owners manual to see where yours is supposed to be. 125psi should be no problem and it should have info on setting the relief.
Contra todo mal, mezcal; contra todo bien, también
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Re: Compressor Help (OT)
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Joined: Feb 2007
Posts: 23,207 Likes: 58
Fe Butt
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Fe Butt
Joined: Feb 2007
Posts: 23,207 Likes: 58 |
Does seem to either be a bad pressure safety valve or you have the compressor set to kick off above it's rated pressure. If the rest of the compressor is OK for the higher pressure then just replace the valve with a higher rated one.
I have an old one lunger from the 50s that kicks off at 150psi and on at 125 psi. I have never done anything but change the oil and bearings in the electric motor once. That thing sees very heavy use for many years. It was in a junkyard I worked at and have been friends with the owners since I was about 14. When the bearins started making noise they sold it to me for $100 and the electric motor shop went through the motor for another $100 and fixed the bearings. Only other work it needed was a good cleaning. been using it myself now for about 12 years. I have another one just like it except gas powered also in perfect working order. It will probably out last me.
I learned all I need to know about life by killing smart people and eating their brains.
Eat right ,Exercise ,Stay fit, Die Anyway!
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Re: Compressor Help (OT)
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Joined: Jul 2007
Posts: 234
Adjunct
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Adjunct
Joined: Jul 2007
Posts: 234 |
Typically there is a valve plate assembly. One valve opens to let air in then closes on the compression stroke, the other (to the receiver) opens on the compression stroke and closes on the intake stroke. Ok so far, this is the obvious.
There is another valve that automatically releases pressure on the head of the unit each time the pressure switch stops the motor. This allows the motor to restart with zero head pressure. This is the hiss of air that you normally hear when the motor stops. This is the "bleeder valve" you are talking about. It always released air, just not the whole tank. I think your problem is with the valve plate in teh head.
Try this:
1) Turn compressor on and as you get to around 70psi, pull the plug.
2) Does it hold pressure. If no the bleeder switch is stuffed. If yes, leave unplugged and turn the compressor of using the switch. A small amount of air should released from the head. If all air is released, you "probably" have a problem with the valve plate in the head.
Adventure before Dementia...
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Re: Compressor Help (OT)
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Joined: Jan 2005
Posts: 5,537
Check Pants
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OP
Check Pants
Joined: Jan 2005
Posts: 5,537 |
Midlife gets the prize it appears. I tossed my problem over on the "Garage Journal" forum as well. A few guys had these Harbor-Freight compressors and have had to clean and/or replace the check valve out of the tank, that is in hte line before that switch bleeder valve. I'll try cleaning it this evening, they believe dirt or other got into it sticking it up, constanstly sending air to that switch bleeder. Here's one reply: This is exactly the problem. The check valve usually will get a little piece of trash in it and stick open allowing the air in the tank to bleed off and drain the tank. The air is coming out of the pressure pop off valve that allows the 'head' pressure to bleed off after the contactor has opened. This allows the compressor to start up quickly the next time the contactor closes and does not have to fight or 'strain' against the pressure of the tank. Turn the breaker off for the compressor, drain the tank and remove the line going from the pressure pop off on the contactor assembly to the check valve on the tank and then remove the check valve that is screwed into the tank. Some check valves have a small internal snap ring that you can take apart and clean the seat then reassemble and reinstall. I generally keep a spare on hand at work because it happens every several months or so. I throw the spare in and then disassemle and clean the spare and throw it into the toolbox for next time. Quote:
Typically there is a valve plate assembly. One valve opens to let air in then closes on the compression stroke, the other (to the receiver) opens on the compression stroke and closes on the intake stroke. Ok so far, this is the obvious.
There is another valve that automatically releases pressure on the head of the unit each time the pressure switch stops the motor. This allows the motor to restart with zero head pressure. This is the hiss of air that you normally hear when the motor stops. This is the "bleeder valve" you are talking about. It always released air, just not the whole tank. I think your problem is with the valve plate in teh head.
Try this:
1) Turn compressor on and as you get to around 70psi, pull the plug.
2) Does it hold pressure. If no the bleeder switch is stuffed. If yes, leave unplugged and turn the compressor of using the switch. A small amount of air should released from the head. If all air is released, you "probably" have a problem with the valve plate in the head.
Last edited by ssjones; 11/09/2009 8:14 AM.
Al
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Re: Compressor Help (OT)
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Joined: Jan 2005
Posts: 5,537
Check Pants
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OP
Check Pants
Joined: Jan 2005
Posts: 5,537 |
Problem solved. I found this piece of metal on the rubber plug of that bleeder valve:  Wow, what a major hassle for something that would have taken me 30 seconds to fix had I only asked when the problem first occurred. I guess they call that "a lesson". Now I have to take it all apart to properly seal all the fittings, there's another 30 minutes into this thing. Thanks again for the replies and good information. My compressor is up and running just in time to start nailing trim in our basement...
Al
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Re: Compressor Help (OT)
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Joined: Feb 2007
Posts: 23,207 Likes: 58
Fe Butt
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Fe Butt
Joined: Feb 2007
Posts: 23,207 Likes: 58 |
I would want to know where the metal came from while still under warranty.
I learned all I need to know about life by killing smart people and eating their brains.
Eat right ,Exercise ,Stay fit, Die Anyway!
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Re: Compressor Help (OT)
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Joined: Jan 2005
Posts: 5,537
Check Pants
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OP
Check Pants
Joined: Jan 2005
Posts: 5,537 |
Quote:
I would want to know where the metal came from while still under warranty.
Yeah, so would I, but since it's Harbor Freight, the warranty was about 35 seconds... (actually, I've had it over a year, $150 compressor) It was just a tiny flake, maybe a paint type flake, but enough to let a crack of air in. The guys on the Garage Journal (great web forum, btw)said I'll need to clear that from dirt/grit every couple of months.
I just buttoned her all back up, letting the pipe compound dry on the joints. Hopefully air-tight by tomorrow AM.
Al
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Re: Compressor Help (OT)
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Joined: Jul 2007
Posts: 234
Adjunct
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Adjunct
Joined: Jul 2007
Posts: 234 |
Quote:
I would want to know where the metal came from while still under warranty.
Normally just a bit of swarf from improper cleaning after machining. Or a little chip from the casting that came off under load. Probably came from inside the head (casting) and during one of its shutdown cycles it blew out and got stuck in the valve. Was it a brand name or the Harbour freight cheap China stuff?. Chinese Castings are still fairly poor especially on the lower cost items.
Change the oil, tighten the head bolts (not overtight) after a few hours of operation, and drain the receiver (air tank) every now and then using the petcock at the base of the tank and it should last for a long time.
Adventure before Dementia...
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Re: Compressor Help (OT)
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Joined: Jan 2005
Posts: 5,537
Check Pants
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OP
Check Pants
Joined: Jan 2005
Posts: 5,537 |
Made in China. The replacement switch came from China as well. I haven't got it quite sealed up correctly. I used Oatey "Great White Paste" this time. When I first put it back together, I used waterpump RTV, which sealed and dried hard. This paste didn't harden and it's leaking around the extra ports on the switch. Gee, I'm getting tired of taking this thing apart! Good reminder to change the oil in it. Good reminder Quote:
Quote:
I would want to know where the metal came from while still under warranty.
Normally just a bit of swarf from improper cleaning after machining. Or a little chip from the casting that came off under load. Probably came from inside the head (casting) and during one of its shutdown cycles it blew out and got stuck in the valve. Was it a brand name or the Harbour freight cheap China stuff?. Chinese Castings are still fairly poor especially on the lower cost items.
Change the oil, tighten the head bolts (not overtight) after a few hours of operation, and drain the receiver (air tank) every now and then using the petcock at the base of the tank and it should last for a long time.
Al
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Re: Compressor Help (OT)
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Joined: Feb 2007
Posts: 23,207 Likes: 58
Fe Butt
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Fe Butt
Joined: Feb 2007
Posts: 23,207 Likes: 58 |
I use teflon tape on that typw of application.
I learned all I need to know about life by killing smart people and eating their brains.
Eat right ,Exercise ,Stay fit, Die Anyway!
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Re: Compressor Help (OT)
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Joined: Jan 2005
Posts: 5,537
Check Pants
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OP
Check Pants
Joined: Jan 2005
Posts: 5,537 |
All tight, the RTV worked. The one fitting that was leaking, was the first one to get white paste from the new tube. Maybe I didn't mix up the tube enough. The other fittings with the white paste are air tight. At any rate, she holds air now.
Al
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