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I have replaced my pressure switch with a Pressuremate 034 -0197RP. When the pressure reaches the 130 psi lever the motor is shut off and air starts coming from the pressure switch. When the pressure leaks down to 90 psi the motor is switched on and the air leak stops. This is the second switch I have installed. What’s happening? So says a posting from “rffs1ham”.
We can feel your frustration from here!
The Powermate Vx 034-0197RP Pressure Switch is a model of the well recognized Condor 11 pressure switch, a photo of which appears below.
What we think you’ve got is a bum tank check valve. The reason for that is, when the pressure switch trips to off, stopping the power flow to the compressor motor, the unloader valve is tripped open at the same time. This allows any air that may be trapped over the piston to escape.
If you have a leaky or failed tank check valve, along with the air that comes off the piston head, all the air from the tank will leak out over time too. When that happens, if the compressor is plugged in, it will start, build up tank pressure to cut off, the compressor will start, and the tank air will leak out again until the compressor restarts. A vicious circle.
As to your additional question “Is the unloader valve in the pressure switch?”, looking a the image of the pressure switch you referred to, the unloader valve for this pressure switch appears to be internal, and the unloader valve tube will contact via a quick-connect fitting on the bottom of this switch.
Another question: Is there a check valve in the 1/2 in. line that feeds the tank? I have an external pressure switch that had the unloader outside of the pressure switch. I’m confused with the what the tank check valve is. Is it’s function to keep air from the 1/2 in. feed line to the tank and flowing through the compressor and through the 1/4 in. line that goes to the unloader valve?
The answer to that is found in detail on the Compressor Tank Check Valve linked from this page.
Depending on your compressor make, and remember, the part number you provided is the part number for a Condor pressure switch, not the compressor make or model, the tank check valve is typically located where the line from the pump enters the tank. The small line from the tank check valve fitting that runs over to the pressure switch unloader valve is the unloader vent line. It empties air from the pump to the tank check valve. It’s the tank check valve that is supposed to keep all the compressed air in the tank until it is used by an air tool or air device.