Motor Problems

another possibility comes to mind.
inside the motor, on the side opposing the shaft end, there is the centrifugal start switch.
the centrifugal start switch effectively switches the start capacitor in and out of the starting circuit.
it is a normally closed set of contacts that is controlled by flyweights and spring tension.
when the motor gets to about 80% of it's nameplate RPM during use, the start capacitor circuit drops out because the flyweights open the circuit.
if there is a burned or otherwise faulty connection or contact, the circuit will not function as intended, also giving the aforementioned symptoms

i have seen many failures of this type as well
 
Quincy compressors normally don't use a check valve at the tank. That function is controlled at the pump. I would take the motor in and have it checked out, if you have someone locally available. Like Doc said, the centrifugal switch could be the culprit. Mike
1543672276589.png
 
Wow Guys, thanks for all the responses. It does look like a new motor is in my future:( Taking it to a shop is not much of an option. Most of the shops around here are backed up. The last time I took a motor in, it was going to take a month for them to get to it. The estimated cost was close to the cost of a new motor:confused:
I need a running compressor. I have now been without one for over a week.
Thanks again
Randy
 
If your compressor is belt drive, simply double the motor pulley size to run the pump at its correct speed.

True, but I can't quite fit double the pulley size in the space available, more like about 150%. But the compressor actually serves my general shop air needs as it is, that and I didn't want to spend $130 for a new pulley. If I do need more air I just switch in the backup 5 HP compressor. :)
 
My first guess would be the start capacitor. A 5hp motor would have a switched start capacitor and a run capacitor. It is very common for the centrifugal switch to jam and not switch out the start cap, 30ms and the start cap is fried.

Pull the capacitor out and use an ohm meter on high range the reading should start low and slowly raise to infinity.
 
Back
Top