Charge Air Pro pressure switch issue

I have a old Charge air pro compressor by Ingersoll-Rand with a 5 hp 240V motor.

The factory installed telemecanigue pressure switch went bad. i replaced it with a Condor 3FWF9 grainger item number pressure switch. www.grainger.com

Once the compressor starts building pressure air flows out the unloader valve at a high steady rate.

If i turn the compressor off the check valve closes and air stops leaking. once i turn the compressor back on, air again purges.

The problem seems to be completly backwards. I understand that once the tank pressure builds there should be a burst to relief head pressure.

My compressor just bypasses until power is removed and then the tank holds pressure. I thought i had a faulty part so the store sent me a replacement. Both switch have the same issue. I'm lost! Thanks for the help.

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Bill says...

A couple of things come to mind.

One is that the toggle for the unloader valve is reversed on the new switch so that it's opening when it should be closed and vice versa.

The other is that your tank check valve has a problem.

Cheers,

Bill