Tank Pressure Switch SK-2512 is malfunctioning on my Bostich TrimAir CAP1512-OF compressor. I have been unable to unscrew this switch from the tank (assuming this is normal righthand thread). I feel like if I apply any more force to unscrew it using large visegrips or small pipe wrench, the plastic male-threaded portion of the chrome-plated plastic body on the switch will break. then I will have a bigger mess.

I chatted with "Paula" at Bostich helpline. Paula indicated that the switch is screwed into the tank using a sealant and "it will be hard to remove".

Anybody know any secret to removing this switch, perhaps by dissolving the sealant with acetone although this might dissolve the plastic threaded body) ??? thanks for any help.

Sorry for delay in responding...I was successful in removing the old pressure switch SK-2512 by applying heat to the tank in the area where the pressure switch is threaded in. I used a heat gun with a "focus nozzle" which softened the sealant quite easily.The old switch was badly corroded inside so it seems that was the smoking gun for compressor not shutting off after reaching 150PSI Tank Pressure.

It took me a while to get a replacement pressure switch ("I live in The Sticks") which I received just yesterday. The new switch SK-2016-10 has threads 0.517 Outside Diameter vs. old switch had 0.503 inch which made an impossible fit of the new switch--I barely got 1 row of threads into the tank. So I reduced the diameter on the new switch to around 0.506 and got the new switch threaded-in except about 2 threads. I reassembled the compressor but it still doesn't shut off when reaching 150psi Tank Pressure (then the relief valve releases).

With soap bubbles I determined the new switch is leaking slightly where threaded into the tank. So I suspect that the switch is sensing a bit less than 150psi (due to the leak) when the Relief Valve senses 150psi (and therefore triggers relief).

So my question is what type of sealant should I use (and do I need heat) to reinstall the new pressure switch? I am assuming (maybe wrongly so) that if Teflon Tape is a good solution then the factory would have used Teflon tape to manufacture with initially.

Thanks for any help.

I checked the wiring including the On/Off Switch thoroughly. I can see that the wiring concept is fairly straightforward--the Pressure Switch is in-series on the Black circuit. The Pressure Switch operates Normally Closed when Tank Pressure is low, and is supposed to go Open Circuit when Tank Pressure is high. I have no way of simulating High Tank Pressure for testing the new Pressure Switch, so I can only assume that it functions correctly (i.e. goes to Open Circuit when Tank Pressure reaches/exceeds 150 PSI. I did test/confirm that Pressure Switch is functioning properly as Closed Circuit under Low/No pressure.

So I reinstalled the new Pressure Switch, this time using natural gas grade Plumbers Dope. I will let that cure for 48 hours then reassemble and retest functionality.

Thanks for ongoing advice.

After reinstalling the Pressure Switch and letting the Pipe Dope dry for 48 hours I retested. Using soap bubbles I no longer saw any leaks at the Switch/Tank fitting. Unfortunately the compressor continues to malfunction, i.e. the Relief Valve discharges at Tank Pressure Gauge reading 150psi and the compressor continues to run, repeating the cycle endlessly. I rechecked all the wiring carefully according to the attached Wiring Diagram and Circuit Testing Results.

I am "stumped" at this point. The only explanations I can think of are:

1) the replacement/new Pressure Switch I received is faulty. It could have been faulty as-received (Manufacturing defect escape or Early Life Fail), or possibly got overstressed during assembly (mechanical overstress) or initial retest (electrical overstress--surge upon startup, etc).
2) the Pressure Switch and Relief Valve are "mismatched", i.e for example the Relief Valve discharges at 150 psi but Pressure Switch goes Open Circuit at 152psi. How accurate/precise are these components anyhow?
3) there is something in the wiring that I am overlooking.

Again, thanks for ongoing help.