Pressure relief switch

by Fred Kaier
(Phoenixville PA)

When my SEARS compressor shuts off, air is leaking from the pressure control switch. (brass fitting with an actuator pin on the bottom of the square D switch box) The only part # I can find on the switch is CAC-4336.what is the replacement part and where can I get it?





Bill answers...

Hello Fred:

While air may be leaking from the unloader valve on your pressure switch, I don't think it's either the unloader valve or the pressure switch that is your problem.

There's a check valve in the line from the head to the tank, and it's purpose is to keep the air in the tank once the compressor unloads. If that leaks, all of the air in your tank will bleed out the unloader valve.

Here's more info on this issue.

Cheers,

Bill




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Pressure relief switch

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Apr 15, 2010
 Hitachi EC12 2HP Twin Tank 4 Gallon Compressor
by: Bill

My twin tank Hitachi EC-12 was leaking down thru the unload valve, I think. So I bought a new press switch with new brass unload valve installed it and to my disbelief it does the same thing. In addition, once the tanks are beyond 90 psi the compressor will stall and just hum until I allow the air to bleed down below 40-30 psi. Could it be the check valve, press switch or unloader? Where is the line check-valve located on this Japanese wonder of engineering?

Thanks- Bill

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Bill says...

Howdy Bill.

The check valve is usually located where the line from the compressor head enters the tank. That fitting often has an integral check valve.

Make sure the check valve is working... that should stop the air dumping from the pressure switch, and if that's solved, come back to us with the humming... hmmmm?

Cheers,

Bill

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