How to Solve Ac Compressor Cycles on and off Every 5 Seconds

Nothing’s worse than getting into a hot car with an AC that can’t seem to cool things down. If your car’s AC compressor is constantly turning on and off every 5 seconds, it likely indicates an underlying issue.

Is It Normal For the AC Compressor To Cycle On And Off

Yes, it’s normal for your car’s AC compressor to cycle on and off. It’s the process of how an AC compressor works and cools down the cabin. Every time the air in your car cabin gets hotter, the compressor cycles to cool down until it reaches the temperature you set. 

Generally, an AC compressor cycles on for between 4-10 seconds and off for 15-20 seconds. So Ac Compressor Cycles on and off Every 5 Seconds is Abnormal.

Causes Of AC Compressor Cycling On And Off

Here are the causes of AC compressor cycles on and off every few seconds:

1. Low Refrigerant Charge

When the refrigerant charge in a car AC system is low, the low side pressure will drop below the level the compressor can maintain. This causes the compressor to cycle on and off in order to maintain the pressure balance. This can be a real nuisance, as it can make the car hot and uncomfortable and can also lead to more wear and tear on the compressor. 

Note: Low-side pressure is part of the AC system between the evaporator outlet and compressor inlet. It’s also termed the suction pressure of the AC compressor.

With the engine running and air-conditioning on, the low side pressure on a car AC system should typically be between 25-40 psi. When you increase the engine RPM, the low side pressure decreases and discharge pressure (at the outlet of the compressor) increases.

All air conditioning systems use a closed refrigerant loop that is pressurized to force the refrigerant to flow through the system. If there is a leak in the system, the pressurized refrigerant will be released, causing the refrigerant charge to become low.

How to spot it?

To spot low refrigerant charge in the car AC system, you should check low-side pressure using the pressure gauge kit with the engine running.

The leaks in the car AC system can happen due to:

  • Faulty seal of condenser, evaporator, and compressor
  • Damaged O-rings
  • Worn-out hose

You can recharge the A/C system with a refrigerant that has a dye in it so you can trace all the hoses and connections when the system leaks down again using UV light. You can also pressurize the car AC system with air and spot refrigerant leaks using soapy water.

Moreover, if evaporator coils are icy, it also indicates low refrigerant levels. This is because when the pressure drops inside evaporator coils due to low refrigerant, the moisture in the air accumulates and freezes on the evaporator coils. This is the basic Physics principle. If the pressure is lower, the freezing point of water increases.