air compressor switch wiring

[krallstar]

Not sure if this is the right place. Hey all, new here. I have been reading about wiring the pressure switch and this is what i found. I have an old 30gal Quincy air compressor. Started blowing the high pressure relief valve. After some reading here i find it's the pressure switch. Mine looks original. The mother is a craftsman i can't see any details on the plaque but can see it's a craftsman. The plug end has 3 prongs. But inside the switch, there are only 2 wires. And what i see is someone took the power cable from the motor and opened the covering. They cut the black wire and connected 1 side to M1 on the switch and the other side of the black wire to theL1 terminal. No green ground. And the white wire was left alone. I am pretty sure this is not wired right. I plan on replacing the power cord with a proper 3 prong. Now would i ground the green because the motor side is a 2 wire plug.

 

[wyliesdiesels]

Is this a 120v or 240v motor?

What is the HP rating?

Yes it definitely needs to be grounded. There should be a grounding terminal somewhere on it.

 

[Citation]

Not sure if this is the right place. Hey all, new here. I have been reading about wiring the pressure switch and this is what i found. I have an old 30gal Quincy air compressor. Started blowing the high pressure relief valve. After some reading here i find it's the pressure switch. Mine looks original. The mother is a craftsman i can't see any details on the plaque but can see it's a craftsman. The plug end has 3 prongs. But inside the switch, there are only 2 wires. And what i see is someone took the power cable from the motor and opened the covering. They cut the black wire and connected 1 side to M1 on the switch and the other side of the black wire to theL1 terminal. No green ground. And the white wire was left alone. I am pretty sure this is not wired right. I plan on replacing the power cord with a proper 3 prong. Now would i ground the green because the motor side is a 2 wire plug.

It's absolutely not wired as the switch is meant to be used. I'm going to assume this is a 120V compressor but that doesn't strictly matter. Even if this were a 240V compressor the way I think they wired it up would switch the motor on and off but isn't how the parts are meant to be used.

My guess is they just wired it up as if this were a light switch. That is they connected the neutral wire from the power plug right to the motor then connected the hot wire from the plug to the switch then to the motor. This means the switch only switches the hot side of the motor. This is kind of like how you wire a switch on a lamp cord.

The way the connector is supposed to be used is both the hot and neutral wires from the power cord are supposed to go the line (L) sides of the switch. This way when the switch is off both wires to the motor are disconnected. This probably isn't critical when dealing with a 120V compressor as the neutral wire, in theory, has no voltage on it and, hopefully, the whole compressor is grounded. However, if this were a 240V setup you would have one "hot" wire connected to the motor at all times, even when the motor was off.

The up side is pressure switches are largely universal and most are just as happy with 240V as 120V.

$25 https://www.amazon.com/dp/B008JVM45G/?tag=atomicindus08-20

$10 https://www.amazon.com/dp/B07G36PGSV/?tag=atomicindus08-20

Odds are your motor is under 15A so either of the above is sufficient for the voltage and current. Other things to look for is do you need an unloader valve and how are your wires run. The Condor (Powermate) switch is part of a family used on many compressors. The differences are where the wires come in (holes in the sides for armored wire or bottom clamps or flexible wire), does it have an unloader valve, what is the preset pressure range. Also, with likely all of these switches you can change the pressure range so a 175 psi switch can be dialed down to a 120 psi switch with no issues.