Compressor Pressure Switch ..2


This is the second page in the series on Compressor Pressure Switches. Here is page one about compressor pressure switches.

We continue by chatting about parts of the compressor pressure switch, including those that have an unloader valve as part of their mechanism.

The unloader valve is typically located on the side of the pressure switch and it is activated by by the cycling of pressure switch points as they open to stop power flow to the motor circuit, and close to resume power to the motor. Other pressure switches have an internal unloader that is connected to the tube from the tank check valve by a fitting on the underside of the switch.

Unloader Valve



pressure switch 2 - pressure switch unloader valve

In the photo you can see the brass colored unloader valve on the side of the pressure switch.

This type of unloader valve is toggled by a lever that is protruding from the side of the switch. That lever moves up and down as the pressure switch trips on and off, and in so doing, operates the unloader valve actuator by depressing or releasing the pin, which can be seen protruding down from the bottom of the valve.

This page provides detailed information about the compressor Unloader Valve.

Troubleshooting The Pressure Switch


If you are not sure if your pressure switch is working, first thing to do is unplug the compressor, pull the cover, and then bleed all the air out of the compressor tank. If the pressure in the tank is higher than the cut in pressure of the switch, the switch will not trip. As the pressure drops it will reach and lower past the cut in pressure of that switch, and you should be able to see and hear the switch trip.

If the pressure in the tank is below the normal cut in, then plug the compressor in, and use a multi-meter to check and see if voltage is flowing through the switch to the motor. If there is no pressure in the tank, the switch should have tripped to ON, and power should be flowing. If it is not, then perhaps the pressure switch is pooched.

There are a couple of issues with pressure switches that are common problems regardless of the brand of compressor they are installed on.

One of those problems is often confused as a pressure switch or unloader valve leak. In the event your pressure switch or unloader valve is bleeding air constantly, the problem may not be either. The compressor check valve may be the issue. Read about that issue and how to fix it here.

If you are still having trouble with your compressor pressure switch, here is a pressure switch troubleshooting page that has lots of postings from folks that have a compressor switch problem, a lot of advice you can read and comment on, and a place for you to post your own question if the answers there do not suffice.

If you diagnose your compressor pressure switch as having failed, here's how to go about selecting a new one.