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I have an older Fini Shuttle direct drive oil compressor. I am getting leaking air at (5) in the photo, which I think is the pressure relief valve. It only leaks while it is pumping, once it eventually reaches pressure and shuts off, or if I manually shut it off, then it behaves normally and does not leak air.

A new Fini Shuttle air compressor
A new Fini Shuttle air compressor

Where should I look to resolve this? Does this have anything to do with the back flow preventer (2)? Also why is there 2 cut off adjustments (3 & 4)? I think (5) is the differential adjust. Thanks….

Condor MD2 pressure switch
Condor MD2 pressure switch

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Howdy, and thanks for writing in.

I tend to agree that the air is leaking from the unloader valve. Typically, if the air leaks out of the unloader while the compressor is running, then it’s the unloader valve itself that is at fault.

If air were bleeding out of the unloader valve with the compressor stopped then I would look to the tank check valve leaking (what you call back flow preventer) as the culprit.

Here is more information on the operation of the Condor pressure switch.