So you have finally tracked down a great deal on an air compressor with a faulty pressure switch or perhaps you just need to replace one. Either way it is time for a new Air Compressor Pressure Switch.
You will need to get the following tools and parts to do this relatively simple repair and by doing so avoid a costly repair bill from a repairman: A correctly rated replacement Air Compressor Pressure Switch, Teflon tape, a crescent wrench, wire strippers, appropriate screwdrivers, and a 1/4” pipe nipple if you can’t reuse the existing one.
Cut all power to your air compressor by either tripping the breaker or unplugging it. Make sure that the tank is empty by slowly opening the bleeder valve to release all pressure. Carefully remove the existing Air Compressor Pressure Switch from your compressor. There should never be a valve installed between the tank and the switch. There is a short pipe nipple, usually 1/4”, already installed on your tank for the Air Compressor Pressure Switch.
Open up the Teflon tape and wrap two to three wraps over the male side of the pipe threads. Twist on the female fitting of your replacement Air Compressor Pressure Switch to the nipple. Gently tighten the connection with your crescent wrench to ensure it is not cross threaded as this will cause a slow leak and keep your compressor running all the time. After it is securely tightened with the wrench, open the cover plate of the switch.
Inside the switch housing there are four contacts, minute copper dots that make up the electrical circuit. When the switch is made up, these contacts allow the compressor to run until correct pressure has been reached. Each of these contacts is linked to a small screw that tightens down onto the correct wire. Using your wire strippers, remove approximately 1 inch of the insulation from your wire. Be careful not to use a smaller wire stripper as this can cause under cutting of the copper wire. This can cause damage to the wire and possibly cause a fire hazard or damage your air compressor. Now that you have the wire stripped ends, locate the two wires running to the motor and the two wires that are your incoming power.
Make certain to match wire color as much as possible so that it is wired correctly. Red to Red (if 240 V AC), Black to Black, White to White and hook up your ground wires.
Use a proper sized screwdriver to loosen the contact screws on the line side of your switch. Insert the power wire under the left side of the screw terminal so that the wire will be pulled under the screw as you tighten it. Repeat this on the other side of the switch that is your motor side, it may be marked as load side.
Now close up your switch housing. Close your manual relief valve and restore power. Turn your compressor on and marvel as it roars to life.