Quincy QT-5 Compressor Problem: Please Help Diagnose

[-Brent-]

I picked up a used Quincy Qt-5 last year and after some wiring work (PO bypassed the mag starter and went directly to the pressure switch) it's been great. However, this weekend it's developed an issue that I'll do my best to describe.

It started off as a short lasting screech which I assumed was the belt. Now, as it increases pressure (say after 130 psi) it develops a really loud screech and it (the pump and motor) slows down and (it may just be me) but it seems like it is going to pop the breaker. I didn't let it get that far.

I did a visual inspection and felt around, the motor was hot, nothing smoking, no weird smells, etc. I checked the oil, it's where it should be.

I fired it up again and in trying to isolate where the screech was coming from I pushed on the back of the motor and the screech disappeared.

The belt is good and it's not loose. There's very little play in the belt.

Because I was working on a different project I didn't do anything else with the compressor.

I'd love your thoughts on this. I hope my explanation was clear.

Thanks,

Brent

 

[-Brent-]

Also, this may need to be known. It doesn't unload with the Psssssh sound, instead it was ******* out the little weep hole on the unloader. I have a check valve on order.

 

[Z2V]

If you pushed on the back of the motor and the noise stopped I'd say you narrowed it down to that motor. You could take the belts off and spin the motor by hand and you might feel a bad bearing. Some motors have a centrifugal speed switch on the end of the motor, if it is gummed up and not kicking out that could cause noise. I'd bet on bad bearing though.
I just bought new Lesson 5 hp and its in shop getting this switch fixed, new motor, never used. That's a story for another day though.

 

[930dreamer]

Could it be a run cap going out?

 

[bodyguy16]

We had a similar problem at work amd ot turned out being the belts were visually sound but upon further inspection if you were to squeeze a folded section in your hand they would snap. Double check the belts to eliminate that if not already done.

Sent from my SM-G903W using Tapatalk

 

[matt_i]

I would also recommend replacing the belt as an "easy" thing you can do.

I would also take a look at the end-cap on the motor. If its a TEFC motor with a fan inside a stamped sheetmetal cage, if the cap tips just a bit, the fan could surely touch the inside of the housing and might rub. I realize a lot of compressors have the fan blades cast into the compressor pulley, can't recall right now what electric motors are used...

If your motor has grease zerks you could try that, but I would not put more than 1 shot into either end. They need like 1 shot every 10 years and any overflow/pushout is all directed inside of the motor....