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

2. Overpressuzied Car AC System

The AC compressor is like the heart of your car’s AC system. It’s responsible for pumping the refrigerant throughout the system, so the air inside your car can be cooled.

But when the compressor is overpressurized, it has to work harder to keep the refrigerant moving, resulting in the compressor cycling on and off every five seconds. 

The first thing to check if your car’s AC is cycling on and off every five seconds is the high-side pressure. If the high-side pressure is too high, it can cause short cycling of the compressor.

Note: The high-pressure side is the region between the compressor discharge and evaporator inlet.

With the engine running and the AC compressor engaged, the high-side pressure is around 200 to 250 psi at 90 degrees Fahrenheit ambient temperature. When you increase engine RPM, the high-side pressure of the AC compressor also increases as the AC compressor rotates at a higher speed. This is because the AC compressor is directly connected to the engine’s crankshaft. Due to this reason, the AC compressor is disengaged when you rev too high to prevent the car AC system from overpressurizing.

How to spot it?

When an air conditioning system is overpressurized, it means the high-side pressure is too high. This is usually caused by a blockage in the air conditioning system, such as a clogged condenser or a faulty expansion valve.

When the pressure is too high, the compressor has to work harder to cool the air, which can cause it to cycle on and off every five seconds. 

So, in short, the car AC system is overpressurized and cycles every few seconds due to the following reasons:

  • Clogged expansion valve
  • Clogged condenser
  • Malfunctioning condenser fan
  • Overcharging of refrigerant

The purpose of an expansion valve is to cool the refrigerant and reduce its pressure. If the expansion valve is clogged with dirt and other contaminants, the compressor has to work hard to flow refrigerant through it. Due to this reason, high-side pressure increases. The same is the case with the condenser. 

The purpose of a condenser fan is to blow air over the condenser to cool down hot refrigerant and convert it into a liquid state after it is pressurized by the compressor.

If the condenser fan is clogged or malfunctioning, it will not run properly. As a result, the condenser couldn’t get rid of the heat of the refrigerant, causing an increase in pressure in the AC system.

Similarly, if you’ve overcharged the car AC system with refrigerant, it will cause an increase in pressure.

Usually, the signs of an overcharged AC system are loud squealing noises from the compressor pulley. So, in that case, you should purge the AC system and charge it with the proper amount of refrigerant recommended by the manufacturer.