# Compressor Maintenance



## Karl_T (Oct 22, 2015)

I bought a Quincy 7.5 hp air compressor at an auction.

Works fine from cold start with no air in tank. When the air pressure drops to restart the unit, the motor stalls. This tells me the unloader valves must not be working. Anybody know of a repair manual, trouble shooting guide, or have suggestions on what to look for. I have zero understanding of how this subsystem works.

Karl


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## JimDawson (Oct 22, 2015)

Is there a small tube running to a valve under the pressure switch?

The attached file might help


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## Firestopper (Oct 23, 2015)

A bad check vavlve could also cause this symptom. This CV is located at the end of the larger tube that feeds air from the pump to the tank. If it leaks, your heads can have tank pressure resulting in high load starts/stall.


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## Karl_T (Oct 23, 2015)

Thanks for the manual. Also check valve makes sense, I can hear a small air leak that must be going back into the compressor head cause soap bubbles can't find it.


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