What is a Pitted Contactor?


A contactor is an electrical relay that controls the flow of electricity to components in the AC unit. The contactor sends voltage to the condenser and outdoor fan motor. Voltage from the thermostat is sent to the contactor and is registered by the contactor’s side terminals. Power is applied to the contactor’s lower terminals and leads from the compressor and fan motor are connected to the top terminals. When the thermostat calls for either heating or cooling, a magnetic action forces a connection from the contactor’s volt side (line side) to the side where the compressor and fan motor are connected (load side). When the thermostat stops calling for action, the contactor opens and stops all power to the equipment.


Pitting is a deterioration process that happens to metals and in this case, contactors when they have been exposed over a period of time to excessive voltage and heat. The pitting eventually creates a surface wherein adequate contact and transfer of electricity is unobtainable, rendering them ineffective and in need of replacement.

Why is this important?

Pitted Contactors can cause the unit to fail and diminish the capacity of the AC unit to cool your dwelling. Typically, when contactors are pitted and burnt they will start sticking. When they stick, they create a circuit wherein electricity is constantly sent to the compressor. If this circuit is left on for a long period of time, it will allow liquid refrigerant to flow into the compressor. Compressors are designed to pump gaseous refrigerant and will be ruined as it will attempt to compress the liquid.



Don JohnsonDon Johnson is the President of Freedom Heating and Cooling in Birmingham, Alabama which offers home owners tools including:
9 Things to Check Before Calling for Service on Your Air Conditioner or Furnace”,  a resource to help home owners save on HVAC problems
The Home Owner’s Guide to Hiring a Heating and Air Conditioning Company“, a quick read on how to guarantee you never suffer by hiring the wrong contractor.
The Ultimate Home Owner’s Guide to Designing an HVAC System , a 59-page eBook covering the 9 steps to building a Complete Home Comfort System.   Contact him at 205-444-4444 or connect on facebook or Google +,