Job Smart compressor intermittent motor

by ROD N
(NEW ULM, TX, USA)

I think I bought this at Tractor Supply 3 years ago. So maybe is the same as a Campbell Hausfeld?


Sometimes the motor will run all the way to 120psi, sometimes stops before it gets there, and sometimes won't start to run at all.

In all cases of malfunction the contactor is closed and sending 250VAC through. So it is not a pressure switch problem.

It is not a bad contact problem in the contactor. And it is not a bad connection, at least up to and through the contactor. I see the 250VAC there on the output.

However, with the cowling off the motor, I do not see 250VAC on any connection on either capacitor nor on the centrifugal start switch, when it fails to run. So apparently there is some connection or switch device in or at the motor itself where the black wire is open.

Wiggling wires around the motor and motor windings has not produced a hint of a loose connection.

Admittedly I have not done too much of that because I don't want it to start and have the fan hurt me.

I suspected there are some high temp switches embedded in the windings that may malfunction. When the motor stops or does not start, using sense of touch, everything is relatively cold, so I do not suspect there is actually an over-temperature problem.

I have no reason to suspect the centrifugal switch because it seems to work...when the motor doesn't work there's no 250VAC anywhere at the motor but it IS at the output of the contactor.

Next step is to break some tie wraps and rule out intermittent connection in the cable between the contactor and motor, but I wanted to ask about likelihood of a temperature switch in the windings going bad. And if so, where can I buy a replacement.

Or is there some other idea of what can go wrong that is likely... like bad connection with the windings? .. where the connections are inside fiberglass insulation sleeving?

Comments for Job Smart compressor intermittent motor

Click here to add your own comments

Mar 29, 2017
intermittent motor
by: Doug in s.d.ca.

Sounds like you're on track -

When it doesn't start, is it as if there is no power to it, or...

Have you checked the start capacitor itself?

It's possible it's bad internally, as well as the broken wire possibility.

Finally, don't expect there to be 250V (measured) at the cap. That's a peak voltage, if/when it's working, ACROSS the cap.

Good luck.

Click here to add your own comments

Add your own question or comment. It's easy to do. How? Simply click here to return to Jobsmart - Tractor Supply Forum.