How to troubleshoot Central AC Contactor ?

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 440volt 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. Very often the 24 volt coil on the base of the contactor just dies.