Tag: A/C control device

Purpose of the AC cycling switch in my car

Purpose of the A/C cycling switch in my car ?

The A/C cycling switch in my car will control the A/C evaporator core pressure  at a point where the evaporator core surface temperature will be maintained slightly above freezing. This prevents icing of the A/C evaporator core and blockage of airflow due to ice build-up.

Where is the cycling switch located in my car ?

The switch is  mounted on a Schrader valve-type fitting on the low side of the auto ac system usually on the top of the accumulator or close to it.

How the switch work in my car ?

A valve depressor, located inside the threaded end of the switch, presses in on the Schrader valve stem. This allows the suction pressure inside the accumulator to control the operation of the switch according to the temperature and pressure of the a/c refrigerant coming out from the evaporator core. The electrical switch contacts open when the suction pressure drops to (22-25 psi).The contacts close when the suction pressure rises to (39-47 psi). When the A/C cycling switch contacts close, the A/C compressor clutch field coil is energized and it pressurizes the refrigerant inside the Air conditioning system. When the switch contacts open, the A/C compressor clutch field coil is deenergized and compressor operation stops allowing the evaporator to pick up heat from the air inside the vehicle’s cabin and preventing excessive low temperatures on the evaporator core to start freezing up.

How Do A/C switches fail ?

The A/C cycling switch uses internal moving metal part contacts to complete and open the electrical circuit that controls the a/c compressor operation and the temperature and pressure control at the evaporator core and on the low side of the automotive air conditioning system. Over time the contacts wear out and the switch must be replaced. The internal parts of the switch can’t be replaced and is just better to replace the entire cycling switch.

How do you know if your ac switch is bad ?

Some of the symptoms of a failed a/c cycling switch are:

  • A/C system not cooling properly
  • A/C system is not cooling at all
  • Air flow out of the vents greatly reduced
  • Smoke coming out from the vents
  • A/C compressor clutch over cycling


How to replace the A/C cycling switch in your vehicle ?

It is not necessary to recover the system to remove the A/C cycling switch. If you need assistance replacing the A/C cycling switch in your vehicle, Call Us Today and one of our ASE and EPA Certified mechanics will come to you. We have auto ac mechanics near you.

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