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Do I need an unloader valve on my switch

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There is no unloader valve on my compressor shutoff switch?
by: Tom Curler

Dear Bill,
I have a 30 gal Montgomery Wards, 230 volt air compressor that I purchased new in the mid 70’s.

The original pressure switch (manufactures) does not have an unloader switch, nor does the compressor have any plumbing to add one. Every replacement switch I can find has an unloader valve. What is my solution to replacing the pressure switch?


Square D pressure switch
Square D pressure switch

Pressure switch without unloader
by: Bill

Hi Tom…

If you visit Square D Pumptrol Water Pump and Air Compressor Pressure Switches you can find them without unloader valves.


Can I use a switch with an Unloader valve if older compressor did not have one?
by: Ken

Have same situation as Tom with older large dual tank snap on compressor with failing air pressure switch.

The air pressure range is 90-120 and there is no Unloader valve or plumbing for one. Have been looking at the Square D ones (9013FHG59J69) and it seems most have a 2 way pressure relief valve. Is this the same as a Unloader valve?

The main question is could I replace the current switch I have with one that has a Unloader valve and just not hook up the valve or disable the valve somehow?

The compressor is 110 v and still runs well.

Thanks for your help on this it is much appreciated.

By Bill Wade

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