How to Diagnose a Non Working Air Conditioning in a Car

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Is your air conditioning blowing hot air or not blowing at all? This guide will lead you through a full view of checking for problems with your vehicle's air conditioning.

EditSteps

1. 1
   Check if air blows with the fan setting turned to high.

   
   

   • If air is not blowing the A/C blower fan may be bad.
2. 2
   Check that the radiator fan engages when the A/C button is pressed.
   • If the fan does not engage, the A/C system may not be ready or the radiator fan motor may be bad. Continue with the diagnostics.

Check that the compressor engages

1. 1
   Locate the compressor.
   • It's inline with the serpentine belt (the main belt in the engine).
2. 2
   Turn on the A/C.
3. 3
   Check if the compressor's clutch has been engaged.
   • It should begin to spin.
4. 4
   If the clutch engages, the fault is elsewhere.
5. 5
   If the clutch does not engage, check for power to the clutch.

Check that the clutch has power

1. 1
   Test the connector to the clutch.
   • It should have 12VDC when it is engaged (0VDC otherwise).
2. 2
   If the clutch does not have power, check the pressure switch.
3. 3
   If the clutch does have power, the problem may be a bad clutch.

Check that the pressure switch is activated

1. 1
   Locate the pressure switch.
   • The pressure switch is inline with the A/C coolant pipeline.
2. 2
   Remove the cap and connector from the pressure switch.
3. 3
   Test the resistance to the pressure switch.
4. 4
   An "Open" reading:
   • Indicates the pressure switch is not activated.
5. 5
   A "Closed" reading:
   • Indicates the pressure switch has enough pressure behind it to be activated.
6. 6
   If the pressure switch is activated, there is a problem with the electrical and the problem is more complicated.
7. 7
   If the pressure switch is not activated, check for pressure in the system.

Check that the system is pressurized

1. 1
   Locate the test/load valves for the A/C system.
   • They are usually located near the compressor.
2. 2
   Test the pressure readings from the valves.
3. 3
   If there is not any pressure or very low pressure, add refrigerant with dye and test for leaks.
4. 4
   If the pressure is a little low, add more refrigerant to the system and retest the pressure sensor.

Test for refrigerant leaks

1. 1
   Add refrigerant with dye to the system.
2. 2
   Check for leaks by following the pipeline around the engine.
3. 3
   At any signs of leaks, replace or repair the tubing/piping.

   
   

Things You'll Need

• UV leak set (black-light and special glasses) to check for leaking refrigerant
• Multi-meter capable of testing Ohm resistance and Voltage in Direct Current to test electrical
• Cans of RF134a to recharge the system
• A/C Pressure Tester
• sources and citations;

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