Dang Frustrating

Thread Starter

ShockBoy

Joined Oct 27, 2009
186
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?
 

debe

Joined Sep 21, 2010
1,389
What is the pressure at which the relief valve goes of at? Is the pressure switch adjustable? maybe set to high.
 

retched

Joined Dec 5, 2009
5,207
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. ;)
 
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Thread Starter

ShockBoy

Joined Oct 27, 2009
186
What is the pressure at which the relief valve goes of at? Is the pressure switch adjustable? maybe set to high.
It's supposed to shut off at 105 psi and start at 85 psi. Not adjustable
A034 9508 is the part number.
 

Thread Starter

ShockBoy

Joined Oct 27, 2009
186
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. ;)
It's a 2 gal tank and the PRV is rated at 110 psi.
 

debe

Joined Sep 21, 2010
1,389
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.
 

Thread Starter

ShockBoy

Joined Oct 27, 2009
186
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.
Will do, pictures on the way.
 

GetDeviceInfo

Joined Jun 7, 2009
2,192
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.
 

gerty

Joined Aug 30, 2007
1,305
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.
 

someonesdad

Joined Jul 7, 2009
1,583
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.)
 

Thread Starter

ShockBoy

Joined Oct 27, 2009
186
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.)
Thanks for the offer of assistance. I will try to sketch out a schematic from the small circuit board.
 

debe

Joined Sep 21, 2010
1,389
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.
 

shortbus

Joined Sep 30, 2009
10,045
@ 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.
 

Thread Starter

ShockBoy

Joined Oct 27, 2009
186
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?
 
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debe

Joined Sep 21, 2010
1,389
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.
 
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