Pressure switch sticking

by Michael
(Seattle)

I have a 20 gallon compressor with a furnas integrated electric/pressure switch. 50% of the time when you turn the switch, its as if the switch isn't actually connected to anything. I tried adjusting the screw for cut out which helped for a few but then it went back to only turning on and off sometimes. When the switch does work, it seems to cut in and out when it's supposed to. It looks like its something to do with the spring? Any help is much appreciated!

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Bill says...

Michael, drain the tank to zero. Turn on the air compressor. Does it start?

When it runs up to high pressure cut out level, does it stop?

Use the PRV (a good time to test it) to drain the air pressure from the tank back down to the normal cut in level.

Does the pressure switch trip and the motor start?

The cost of a new pressure switch is a fraction of the cost to you in time and aggravation to try and find a part, buy the part, disassemble and reassemble a pressure switch, find out that the repair didn't work, and then go buy another.

Take the short cut.

If the switch is pooched, buy and install a new one.

Nice photo, thanks.

Cheers,

Bill




Comments for
Pressure switch sticking

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Sep 15, 2011
 pressure
by: Anonymous

Bill, I have one more question for you before I go get a new switch. When the tank is 3/4 or so full the switch works great. But when it gets to full pressure the switch won't turn over. It's as if the physical switch itself becomes disconnected from the rest of the pressure switch. And then I'll use it for a while, let it sit, and viola it works. Any ideas? Thanks again, I really appreciate it.

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Michael, based on the symptoms provided, and assuming that it is the switch itself that is not tripping open and closed based on the system pressure (an not, for example, the motor being sluggish on start up at higher pressures ) then it pretty much has to be the pressure switch. They operate on a spring and a diaphragm and both of these are wear items. Good luck.
Sep 12, 2011
 switch
by: Michael

Thanks Bill. It cuts in and out when its supposed to. I pulled the switch off and it works fine disconnected but with air hooked up it gets stuck in the on or off position. Kinda weird. Any advice on where to buy furnas switches?

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As long as the cut in and cut out pressures are similar, and you can mount the new switch and the unloader works, any brand switch will do. Your pressure switch brand is common, and compressor sellers should stock it.

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