Air conditioning troubleshooting

Before servicing or diagnosing an Air conditioning A/C system there are preliminary checks that should take place.

These include:

  • Checking for visual hose damage and chaffing.
  • Compressor cycles on and off.
  • Evaporator drain hose not blocked.
  • Ensure the condenser cooling fins are not blocked with obstructions such as insects, leaves or grass.
  • Condenser fan operates and runs in correct direction.
  • Heater turned off in the full cold mode position.
  • Blower fan has all speeds operational.
  • Air mix door fully closed.
  • Inspect drive belts for correct tension and damage.
  • Dash vents open and close fully.
  • No air leaks between evaporator case and heater case.

Air conditioning system is noisy

The noise heard when the Air conditioning A/C system is first turned on is not due to a defect. In the event of persistent noise, check for the presence of one of the following malfunction causes and apply the corresponding solution.

Cause Solutions
Belt worn or slipped. Check the wear and tension of the belt.
Belt idler pulley is noisy. Replace it.
Electric clutch plate lipped. Make sure that the distance between the compressor pulley and electric clutch is 0.3-0.5mm.
Vibration and resonance of the compressor support plate. Make sure the bolts are tight and the plate is properly positioned.
Expansion valve “whistles”. If the noise persist, replace the valve.

In The following instances, a few defective components of the A/C system create an incorrect inlet and outlet pressure. This phenomenon causes noise in the compressor that is actually due to one of the causes listed below and NOT to the compressor itself.

  • Incorrect amount of refrigerant (30-35% more or 70-75% less).
  • Expansion valve stuck shut or blocked.
  • Compressor displacement regular valve defective (for variable-displacement compressors only).
  • Clogging in the A/C system circuit
  • Filter saturated with moisture.

Air con system emits unpleasant odours

Under certain conditions, moulds and bacteria (normally present in the air) may form on the surface of the evaporator core, causing an unpleasant odour inside the vehicle.

  • Use an antibacterial product to the treat the evaporator.
  • Advise the customer to turn off the Air conditioning A/C system a few minutes before shutting off the vehicle, leaving the blower fan running (this will dry the evaporator core from the moisture that encourages bacteria growth).

Condenser does not dissipate enough heat

Cause Solutions
Air flow blocked by dirt accumulated on the heat exchangers; water radiator, condenser. Clean the radiator and condenser throughly.
The pressure switch or water temperature bulb are not tripped at the correct pressure and temperature levels. Cut out the controls using the appropriate electrical connection. Replace the defective part if necessary.
The electric fan does not work. Power the electric fan directly. Replace if it still does not work.
Incorrect functioning by the electric fan (incorrect rotation direction). The fan must be “suction” type when placed between the heat exchangers and the engine, and “blowing” type if placed between the heat exchangers and outside air intake.
Engine water overheated. Make sure the original engine cooling system is working properly.
Condenser not positioned correctly. Make sure that the distance between the radiator and condenser is 15-20mm, if present the air ducts must be correctly positioned.