Bartlettairheat Blog

What is a contactor?

A contactor is an electrically controlled switch used to switch on power circuits. Its almost like a relay but has higher power settings. Contactors are controlled by a circuit. The contactor controls the air conditioner. It creates a magnetic field that pulls in a set of contacts to power another device. The magnetic field pulls the plunger to the middle of the contactor and allows it to close. Each set of contactors is made up of two components, one fixed and one movable. These components are also known as poles. The movable contact is connected to a plunger that moves to the fixed pole completing the electrical circuit providing power to the air conditioner. When the thermostat decides cooling is no longer needed, the magnetic field flowing through the contactor is shut off releasing the plunger and opening the contactor. The contactors ends are made of steel plated in silver. After awhile the silver wears away exposing the steel and the steel welds itself together at times. If it gets stuck like that temporarily, just giving it a good tap will fix the issue.You should replace your contactor about every two years as a part of routine maintenance.

Normal failure of the contactors is they stick closed. The outside condensing unit will not shut off when the contactor is stuck closed. When this happens, you will often find ice on the condensing lines outside. An electric arc can also happen if the contactor sticks closed. When it is sticking like that, it needs to be replaced or you can do a lot of damage to your unit. Contactors also fail to close at times and this is due to bugs and mice. Spiders and earwigs love to crawl into the contactors and short them out. Electrical shorts can also plague contactors. When coils are shorted, grounded, or open it the contactor can fail electrically. Bartlett Heating and Air can fix and diagnose your contactor. We do not recommended changing the contactor out on your own because you can get shocked. Call Bartlett Heating and Air today to have all your heating and air needs taken care of.