craftsman 175psi 80 gal tank compressor wont turn off

by Thomas
(Senatobia, Ms)

craftsman 175psi 80 gal tank. replaced the pressure switch and releif valve. continues to run and releif valve starts popping/releasing air. this is on the big pipe that runs from compressor back into compressor. not line from compressor to tank. releif valve releases at about 90psi tank pressure


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Bill says....

Hello Thomas. I must confess, this puzzles me; "this is on the big pipe that runs from compressor back into compressor"?

Regardless, the device that cycles the air compressor on and off is the pressure switch, and that's the only device that controls the power flow to the motor.

You say you replaced the pressure switch and the problem remains. Let me ask you, is this a two cylinder compressor, and the line you refer to is the air line between pistons?

That being the case, look to the valve not working in the second piston, it may be preventing ingress of air to the second cylinder, that back pressures the line, and blows the PRV that is normally set below the pressure setting of the PRV that flows from the second air cylinder down to the tank.

If, on the other hand, I'm not even close, I need more details. :-)

Cheers,

Bill

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Oct 02, 2011
relief valve blowing
by: Buster

Sounds like this is a 2 stage compressor, @175psi, and the PRV is on the interstage line between the low pressure piston and the high pressure piston. Like Bill says, the valves in the high pressure head have failed and not allowing the high side piston to put the air in the tank and the low pressure piston is still pushing more air into the high pressure piston and it can't get rid of it, so the pressure builds to the relief point on the interstage pipe and blows off pressure. Sounds like a head overhaul is in order,

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Craftsman compressor won't build past 20 lbs of pressure

by JOHN
(monrovia, ca, usa)

My Craftsman compressor is model #919.155611 It's a 1.5 HP 12 gal permanently lubricated Fusetron type.

I noticed air leaking out of the flow valve, so I replaced it. Nothing changed.
The compressor starts up fine and sounds normal, but stops building around 20 PSI.
It worked fine last week.

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Bill says...

Hello John. You say you noticed air leaking out of the "flow valve" and you replaced it. The term escapes me. What do you mean by a "flow valve" please?

There are many reasons why an air compressor stops building pressure, and a lot of info is available to you if you look at those pages linked from the TROUBLESHOOTING page.

However, it might be something simple, if only I knew what is what you call a flow valve I may be able to pinpoint that.

Cheers,

Bill

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