I have an older (20+ years) "Cast Iron Series" Speedaire compressor.

The problem is that after the compressor pressures up and kicks off the pump the mechanism on the side of the pressure switch commands open the bleeder (unloader) valve. The pressure then slowly leaks out through the bleeder until the turn on pressure is reached and then the tank pressurizes again. This is a tremendous waste of energy and annoying due to the constant hiss of lost pressure.

Can you tell me if the pressure switch is bad based on this description?

If the pressure switch is bad can you tell me how to ascertain the model of the compressor so that I can order a new pressure switch? I do not see any markings or plate that identifies the exact model.

Thank you in advance.

I see what you are saying about the check valve.

Ok, it is older than I thought. Model is 3Z421G.

Can you point me to the correct check valve to purchase?

Thanks.

I have asked the mfgr. for the part number.
I will let you know on Monday.