Common Causes Of Low Suction Pressure

Common Causes Of Low Suction Pressure

Is your car’s A/C system not working properly? It is true that air conditioning issues can get very complicated in automobiles but that does not mean that you can’t troubleshoot the problems yourself. In many cases, you can perform repairs for most of the common problems. This post will provide some insights in dealing with low suction pressure.

Common Causes of Low Suction Pressure

You may wish to check for:

  • Excessive moisture in system
  • Flattened or kinked hose
  • Worn compressor piston
  • Shortage of refrigerant
  • A leaking compressor head gasket
  • A leaking compressor suction valve
  • Debris in expansion valve or screen

How to Fix Low Suction Pressure Issues

  • If there is excessive moisture in system: replace the drier.
  • If you find a flattened or kinked hose: replace the hose.
  • If the compressor pistons have worn out: replace the compressor.
  • If there is a shortage of refrigerant: add refrigerant.
  • If there is a leaking compressor head gasket: replace the head gasket.
  • If there is a leaking compressor suction valve: change the valve plate.
  • If there is debris in the expansion valve or screen: replace the drier.

Which Type of Car A/C Compressors Require Suction Pressure?

  • Vane compressors

Suction pressure is needed in vane type compressors. These compressors are constructed from multiple vanes and cylinders. It features front and back side plates as well as two discharge valves. When the cylinder volume increases due to rotor rotation, refrigerant will flow into the cylinder shaft from the suction port. When the refrigerant is sealed within the cylinder, it will be compressed via the rotation of the rotor. The refrigerant is eventually discharged from the discharge port once the outlet pressure has been reached. In many cases, refrigerant is discharged 10 times for each rotation.

  • Fixed displacement compressors

In fixed displacement swash plate type compressors, they typically comprise a piston that completes a 360 cycle, when the engine is turn on. The ends of those piston intakes are designed to discharge and pressurize refrigerant. When the piston moves to the left, the suction valve will open. This causes a difference in pressure between the insides of the cylinder and the suction shaft that’s located within the housing.

Refrigerant can then enter the cylinder via the suction valve. In some cases, refrigerant is required to flow through a high-pressure pipe. The discharge and suction valves are designed to prevent flow back of the refrigerant. The balance of reliability and characteristics in this type of compressor makes it suited for a wider range of vehicles around the world, including construction equipment, large busses, mini-vans, and other small vehicles.

  • Scroll compressors

These compressors are usually constructed from one rotating and one fixed scroll in an offset spiral configuration. Spaces of varying volume are then formed between the two scrolls via shaft rotation. This process causes refrigerant to be sucked in (it usually flows in from the suction port) and compressed. After about three rotations, the refrigerant is discharged from the discharge port. In many cases, refrigerant is discharged once for each rotation. The compressor is installed in many light and small cars because it is efficient and extremely quiet.