Pressure switch on Campbell Hausfeld air compressor

I have a C/H tank on wheels air compressor. Model #957607 20 gal cast iron series. I bought this compressor new back in "92 and it has been a good one. I forgot and left it plugged in last night and this morning I found that it must have come and ended up tripping the breaker to the outlet I usually plug it into. The outlet that I usually use isn"t just for the compressor and also serves some lights in our mudroom - I have had times that it has tripped the breaker when it comes on and we have lights on in the mudroom. I typically never leave it plugged in over night or when I"m not using it.

Anyway - this morning the breaker is tripped. I reset the breaker the compressor motor hummed - but never started - and then tripped the breaker again. I plugged it in to another outlet (different circuit) and the motor hummed, never started and then tripped that circuit breaker. I removed the belt guard and can spin the Emerson electric motor by hand easily. I used the safety valve to let 1/2 the air out of the tank, gently tapped around the motor and pressure switch assembly with the same results. The red thermal overload button did not pop on the electric motor and I did not smell anything burnt on the motor.

Could I have a bad pressure switch on this? The p/n CW208102AV for the pressure switch has been superceeded to CW301300AJ and looks like the entire assembly with pressure switch and regulator for around $80 or so. The compressor is enough for what I need in the garage and is certainly worth putting some money into.

What should I be checking for before I start throwing parts at it? Much obliged.

Open up the top of the pressure switch. Inside you will find a set of points on a relay sort of thing. Look at them but I do not believe that is the problem since you say the motor hums which says the switch is working. I almost bet that the if it has it that is capacitor is bad. If it does not have the start capacitor then the motor start area is most likely bad. You also might try this being very careful. Pull the belt off the motor and then plug it in and spin the pulley on the motor. If it spins up that way and runs it is the start circuit of the motor that is bad

I would guess that the capacitor is bad. I have the same problem with a Sear's that I have. I just rap the capacitor lightly when that happens and it kicks in and runs. Some times works for a while and sometimes not. I don't use it real often, so have not got in a big hurry to fix.

I will second what tractor300 posted. You just have a bad capacitor. Take the motor off and have it repaired. There are several motor repair shops around me here. I just had a big heavy air compressor motor repaired, 10 hp GE. I just picked it up yesterday. He replaced two capacitors and installed new clips for the capacitors. He charged me $52 total.

Shoot why not just pull the old capacitor off take it to radio shack or motor repair place and buy one then install it. Simple 2 wire set up and you can not install it wrong and the cost is less then $10. But I also told him it was likely to be the capcitor

Many thanks. I figured I didn't have anything to lose, so I wired the motor wires to a plug and tried it. First time - no good just sat there and hummed. I took the end cap off the motor by removing the 4 long threaded bolts and blew it out (with my other little compressor). Put it all back together and tried it one more time and it worked - just sat there and ran like a champ. Reassembled everything back together and it runs up to pressure 125 lbs and shuts off.

I'll get the numbers off the motor and get ahold of the electric motor guy in town so he can make sure it's up to snuff.

I appreciate the feedback - I would have replaced the pressure switch first and then found out that is wasn't the problem. This is why I hang around on here. This website and those on it - are better than hanging around the ice cream cooler at the local gas station like I used to do.

So your saying it does not have the start capacitor set up right??? If it does not then that is an induction start motor and very likely that it will not last long now since it has done that once. If it has a sort of a hump on the top or even 2 humps that is where the capacitor or 2 of them are. Some motors have one some a pair and thy will cause that problem if they are getting bad

Probably had dirt in the starting contacts.

(quoted from post at 20:36:08 07/29/12) Probably had dirt in the starting contacts.

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That or the centrifugal switch stuck.

Dusty

Sorry Old - I didn"t see your reply. Here is what the motor looks like. Thanks again.

Yep capacitor start type motor so yep one or both caps. maybe going bad