Contactor 101

Magnetic relays commonly known as definite purpose contactors are used in a variety of different applications throughout the HVAC and Appliance world. They can have anywhere  from 1 pole or up to 4 poles or more. The coils on them can be 24 volt 120 volt 240 volt or even 440 volt and better. Their main job is to power compressors and fan motors on various equipment. On a home unit the contactor is almost always a 24 volt 2 pole 30 amp one. Some smaller units have what is known as a pole and a half. or 1.5 poles. The coil pulls down only one side of the contactor, while the common leg has a straight bar across it. On home units smaller thermostat wires connect to the 24 volt coil powered by a transformer. When the temp rises the thermostat calls for the contactor to yank down and power up the compressor and fan outside. if those small wires are chewed up by an animal or a weed eater then power to the coil cannot

do its job. Sometimes the coil simply dies like a light bulb. If the coil is open then nothing will happen when the thermostat calls for cooling. Sometimes the contacts on the contactor get burned and fall apart. The coil yanks down the contacts fine but sadly the points are fried. Sometimes a critter will make a home right under the contacts.

                2 pole 30 amp 24 volt contactor cooked  (stick a fork in it, it is done) LOL

 When the weather turns warm the coil yanks down and you have crispy critter and no cooling either. Oh the inside will work but nothing will happen outside until the contactor is replaced. 240 volts will kill you. Make sure to kill the power to outside unit before servicing any part.

Spiffy new contactor (around $25)