Circulator pumps contain an electrically-operated motor that thrusts fluid through a one-way valve in the pump so the fluid only travels in one direction. Your home heating system is a typical example for the use of a circulator pump. Circulator pumps can stop working for several reasons: a blown fuse, bad wiring or a dead motor. Troubleshooting the possible causes in a systematic manner ensures you can find the reason your circulator pump isn't working so you can get it back up and running as soon as possible.
Remove the plug from the socket on the end of the wire that connects to your circulator pump. Unscrew the plug cover with a suitable screwdriver to remove it.
Check the three wires are connected to the plug terminals. If any of them are loose or disconnected, your circulator pump won't work. Reconnect or tighten loose connections. Each plug terminal has a screw, so loosen the screw so you can insert the wire neatly into the hole. Tighten the screw and check the connection is secure.
Remove the fuse from the plug fuse holder. Pry it out with a small screwdriver, as it's difficult to remove using your fingers. Put a new fuse in the fuse holder. Push it in place using your fingers. Ensure the replacement fuse has the same ampere rating as the one you removed.
Replace the plug cover and tighten using a screwdriver. Insert the plug into the socket and turn on the pump. It should work if reconnecting the wires or replacing the fuse was the problem. If it doesn't work, continue troubleshooting.
Remove the plug from the socket. Remove the cover from the circulator pump, unscrewing the screws using a screwdriver. Take off the cover. You will find the circulator pump terminals inside.
Check the wires are connected the same as you did for the plug earlier and reconnect or tighten any loose connections. The wires from the terminal connections go to a transformer box. Check the wires are connected and secure. Wires extend from the other side of the transformer and connect to the circulator motor.
Check the wires are connected and secure as before. If you found any loose or disconnected wires, it's probably the reason why the pump doesn't work, so replace the pump cover then insert the plug into the socket and turn the pump on. If it works, you've solved the problem. If it doesn't work, continue troubleshooting.
Remove the cover from the pump again. Be sure to put on rubber gloves. You need to test the electrical circuit so the power has to be turned on.
Check if electricity is getting to the pump using a voltmeter. Carefully place the sensor on the end of the black wire from the meter onto the terminal block that the wires from the plug connect to first marked "Neu," "Neg," or "-." Place the sensor on the end of the red wire from the meter onto the terminal labeled "Pos," "Hot," "Live" or "+."
Read the voltmeter display. If there is no reading, the cable from the plug to the pump needs replacing. If there's a reading, power is getting to the terminal block and to the transformer. Expect the reading to be about 120 volts.
Place the sensor on the end of the black wire from the meter onto the terminal from the transformer that goes to the pump motor marked "Neg," or "-" to test the transformer. Place the sensor on the end of the red wire from the meter onto the terminal labeled "Pos" or "+."
Read the voltmeter display. If it has a reading, the transformer is working and the pump motor needs replacing. Expect the reading to be in the range of 10 to 30 volts. If there's no reading, the transformer needs replacing.
Replace the circulator pump cover. Remove the plug from the socket.