by Jerrell

It will not shut off at 180 psi anymore.

Pressure switch switch off/on (auto) selector dial has not been working for a while, would just leave it in the on/auto position then just unplug when done.

DeWalt 55146 air compressor


Been working a while this way but recently stop shutting off at 180 psi.

I would have to unplug power to get it to stop. It has gotten to 210 psi before I shut down.

While troubleshooting found that one of the hose coupler on the unit was leaking so replaced it, still got issue.

Since had I had a problem with pressure switch I replaced it.

Unit still will not shut off.

Next let all air out of tank then refilled till both pressure gauges showed 150 psi. Left sitting over night for 12-15 hours to see if had a leak any where. Both gauges still had 150 psi (one was showing 146 but felt this was ok).

Was going to spray all lines and fitting with soapy water to see if I had a leak but not sure if I need to now.

Anyway I am stuck as what my next troubleshooting steps should be. Can anyone help me out please?



Dewalt D55146 type 3 will not shut off
by: Bill

When you use your multi-meter to check the power, is power still flowing from the pressure switch to the motor side even when the tank pressure rises past the normal cut out?

If yes, and assuming that the pressure switch is set to cut out at 185 PSI, then either the switch is pooched, or it’s wired wrong.

If the pressure switch is working, if it’s wired correctly, and if the pressure cut out is 185 PSI, when the tank pressure reaches +/- 5 PSI of 185 PSI the pressure switch will shift to non-passing (trip off), and power will no longer flow to the motor, stopping it.

At this point the tank pressure will no longer rise.


Color me confused
by: Doug in

That pressure switch (a21107) appears to be set to 200PSI.

The model appears to be a 4.5 (as opposed to 2.5) gallon tank.

The tank seems to be rated around 250PSI with a 225PSI safety.

The range on pressure switch is supposed to be +/-10%, so that’d be 180 to 220PSI, just short of the safety valve rating.

So, since replacing the pressure switch, have you let it run up to 220 or whatever the safety valve allows?


by: Jerrell

My bad typo it is a 4.5 gal unit

Yes tank rated at 200 psi

Unit best I remember, always shut off at 180 psi

But 180 or 200 it still does not shut off. One time I let it run up around 220 before unplugging. I do know for a fact that it has never run above 200 until recently.


Switch wired correctly
by: Jerrelll

I am sure pressure switch is wired correctly.

Doing this from memory

Only 2 ground screws one each side of switch

One wire from both side of switch ttired together (idiot proof due to connector type)

2 other wires that are hard to get crossed due to length

BUT when you take about 15 pictures with iPhone prior to disconnecting it is hard to to wire switch wrong.

Have not checked power reading with meter but will check and update

Thanks for feedback




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