Bostitch CAP1512 won't cut off

by Jonathan harris
(bumpass VA.)

Bostitch CAP1512 compressor

Bostitch CAP1512 compressor

Replaced pressure still won't cut off

Comments for Bostitch CAP1512 won't cut off

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Jul 15, 2015
Bostitch CAP 1512
by: Bill

Thanks for your kind words and for taking the time to explain how your "new" pressure switch failed.

It will help other Bostitch compressor owners too, I'm sure.

Bill

Jul 15, 2015
Bostitch CAP 1512 Does not shut off
by: Tom B.

Hi Bill,

Thank you for hosting a very helpful site. I had the same problem where it would not shut off, and the PRV released properly. It did turn out to be the electrical pressure switch. However, I had purchased 2 pressure switches figuring I'd always have a spare. When I put the first replacement in, it still continued to run, with the PRV blowing off. After many other troubleshooting checks (both electrical and mechanical), I was totally frustrated. I ended up putting the second replacement pressure switch in, and it worked. Everything as it was supposed to be.

To recheck my own troubleshooting abilities, I cobbled a fitting that allowed me to put the (nonworking)pressure switch on an air line. I took it to 150 PSI and 160 PSI. It failed to create an open circuit (this would shut off current to the motor, and reestablish a connection at the lower limit). This check sequence allowed me to confirm the first (original) pressure switch was bad, and the second (new) switch was also defective.

My humble diagnosis for failure:

The pressure switch is screwed into the tank in an almost vertical position (electrical connections pointed down/away from the tank). The air inlet for the switch effectively is facing the bottom of the tank. Where does condensation reside? At the bottom of the tank!! Where do you think the water goes?? Right into the inlet port of the pressure switch. What happens when water and steel mix?? RUST.

The first failed pressure switch had very visible rust inside. The second one had rust forming around the fitting. This is a design shortcoming, exacerbated by my receiving a defective switch.

Solution: Leaning to my creative side, I went to Lowes and got a 90 degree brass fitting that fit the tank and received the threaded end of the pressure switch. I "massaged" the fitting (cut and soldered) until it was almost vertical. Since water doesn't run uphill, the tank no longer drains into the inlet port of the switch. This fix was successful, but a lot more effort than it was worth. We'll see how long this lasts...

Thanks again for your hosting this site. I hope my unfortunate experience can shed some light on the problem.

Oct 13, 2014
Bostitch CAP1512 won't cut off
by: Bill

Johnathan, is the pressure in the tank rising past the normal cut out pressure and the PRV is letting go, or is the pressure in the tank not ever getting to the cut out pressure setting?

If the pressure on your Bostitch CAP1512 never gets to the cut out pressure, it's not your pressure switch that's the problem normally, it's to do with other issues.

These other issues are covered on the troubleshooting page about why air compressors run but don't build air pressure.

Have a look at that page, then add any questions as a comment here.

Bill

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