Dang Frustrating

Discussion in 'General Electronics Chat' started by ShockBoy, Apr 5, 2011.

  1. ShockBoy

    Thread Starter Active Member

    Oct 27, 2009
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    Hi all, I was given an air compressor recently and the reason being that it won't shut off. It keeps going until the PRV pops. So it's got to be the pressure switch right? Well unless I got a brand new faulty pressure switch, something else is wrong. Anybody have any ideas?
     
  2. debe

    Well-Known Member

    Sep 21, 2010
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    What is the pressure at which the relief valve goes of at? Is the pressure switch adjustable? maybe set to high.
     
  3. retched

    AAC Fanatic!

    Dec 5, 2009
    5,201
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    There should be a threaded screw adjustment on the pressure switch. Crank it WAAAY the heck down, and set up a disconnect out or the room, so if the em-valve blows, you can yank the power without having to get near the tank.

    Often, the motor/compressor can put air into the tank faster than the oops-valve can let it out. Watch for flying pressure vessel. ;)
     
    Last edited by a moderator: Apr 5, 2011
  4. ShockBoy

    Thread Starter Active Member

    Oct 27, 2009
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    It's supposed to shut off at 105 psi and start at 85 psi. Not adjustable
    A034 9508 is the part number.
     
  5. ShockBoy

    Thread Starter Active Member

    Oct 27, 2009
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    It's a 2 gal tank and the PRV is rated at 110 psi.
     
  6. Jaguarjoe

    Active Member

    Apr 7, 2010
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  7. debe

    Well-Known Member

    Sep 21, 2010
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    The PRV valve pressure is fine. Sounds like the pressure switch is to high to switch off or faulty. Very surprised its not adjustable. When asking for help good clear pictures of things help, say the pressure switch with cover off.
     
  8. ShockBoy

    Thread Starter Active Member

    Oct 27, 2009
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    Will do, pictures on the way.
     
  9. GetDeviceInfo

    Senior Member

    Jun 7, 2009
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    your pressure switch typically has a snap action contact within. can you hear it snap over at or close to the rated pressure setting? Are the terminals accessible, I'd check that it wasn't miss wired.
     
  10. gerty

    AAC Fanatic!

    Aug 30, 2007
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    My first thought is, is it wired correctly. Does the motor run if you take one wire off of the pressure switch? Are both wires to the pressure switch under one screw? ( And yes, I have seen that done).
    Show us a picture or wiring schematic/drawing of what you have, and then we will be able to help.
     
  11. ShockBoy

    Thread Starter Active Member

    Oct 27, 2009
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    Here are a couple of pictures of what I've got.
     
  12. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    Is the 'yellow' component a relay? If so possibly the contacts are welded together?
     
  13. ShockBoy

    Thread Starter Active Member

    Oct 27, 2009
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    The yellow component has two terminals and the markings on it are;
    104k275~x2
    40/085/21
    250~
     
  14. someonesdad

    Senior Member

    Jul 7, 2009
    1,585
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    I'd first suspect the pressure valve, but as someone mentioned, if there's a relay, the contacts could be fused.

    You should take an ohmmeter and sketch out the circuit -- it can't be very complicated. You can take the pressure switch off and test it with another compressor if you can get access to one. I made a handy tester with a precision gauge and regulator that can connect up to such things and perform such measurements -- if you were nearby, I'd give you a hand with it.

    Have you contacted the Coleman factory to see if they can get you a manual or schematic? Of course, given the crappy customer service and general policies in dealing with consumers in the last few decades, do-it-yourselfers are often shunned. Another approach is that you can find local service places who know all about such things and can repair it for a reasonable fee. I've occasionally found that when I drag something I'm working on to a repair business, they'll sometimes have a tech come out from the back and help me. (I make dang sure to give those folks my business.)
     
  15. ShockBoy

    Thread Starter Active Member

    Oct 27, 2009
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    Thanks for the offer of assistance. I will try to sketch out a schematic from the small circuit board.
     
  16. debe

    Well-Known Member

    Sep 21, 2010
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    The small black object screwed in to the tank with 2 white wires is the pressure switch & its a non abjustable type. Howmutch current does the compressor draw? is it 12V DC? I suspect the current draw is to mutch for the switch & is damaged. The yellow oject is a capacitor & the black square is probably a bridge rectifier to protect the fan from rev voltage.
     
  17. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    @ Shockboy, thats(the yellow component) a filter capacitor for the DC voltage for the fan. The black component next to it is probably a bridge rectifier.

    What happens if you disconnect one of the white wires from the switch? That will/should tell you if it's in the pressure switch or the board circuit.
     
  18. ShockBoy

    Thread Starter Active Member

    Oct 27, 2009
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    Disconnected one of the white wires to the pressure switch and it did not turn on. So does that mean I've got ANOTHER bad switch?

    Is there a way to fix the pressure switch? I have no idea what goes on inside one of them. Tap it on the ground, spray lube in it?
     
    Last edited: Apr 6, 2011
  19. debe

    Well-Known Member

    Sep 21, 2010
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    Might be better to buy an adjustable switch. Still question of comp current draw, those switches wouldnt be capable of more than 5A DC @ 12v.
     
  20. ShockBoy

    Thread Starter Active Member

    Oct 27, 2009
    186
    0
    Is it the current draw of the pressure switch, or the whole compressor?
     
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