If you own a car and the air conditioning is not working after years of non-use, it may not be necessary to replace the entire system, despite what some repair shops suggest. In many cases, the problem is related to specific components such as the pressure switch, relay or compressor. In this guide, we will see how to diagnose the problem and, if possible, fix it yourself.
1. Check the refrigerant gas level
- Problem: After years of non-use, the system may have lost some of its refrigerant gas, causing insufficient pressure to activate the compressor.
- Solution: Take your car to a specialist to check the refrigerant pressure and recharge the system if necessary. A pressure switch may prevent the compressor from turning on if the pressure is too low.
Note: A leaky system may indicate micro leaks that require further inspection.
2. Checking the pressure switch
- Problem: The pressure switch is a sensor that monitors the gas pressure. If it is not working properly, the compressor will not start.
- Solution: Use a multimeter to check the continuity of the pressure switch. If defective, replace it with a compatible model.
Tip: Some pressure switches can be temporarily bypassed to see if the compressor starts. This is useful as a diagnostic test only.
3. Inspection of compressor relay
- Problem: The relay that controls the compressor power may be faulty.
- Solution: Consult your vehicle's manual to locate the compressor relay. Try temporarily replacing it with another identical relay in the vehicle, such as the horn or headlight relay, to see if the compressor starts.
Tip: If the compressor works with another relay, replace the original relay.
4. Check wiring and connections
- Problem: Damaged wiring, loose or oxidized connections can interrupt power to the compressor.
- Solution: Visually inspect the wiring connecting the compressor and pressure switch. Look for signs of damage, wear, or corrosion. Use an electrical contact cleaner spray to remove any oxidation.
Note: Be sure to disconnect the battery before working on the electrical wiring.
5. Check the compressor
- Problem: The compressor may be stuck or the electromagnetic clutch may not be working properly.
- Solution: With the engine off, try to manually rotate the compressor pulley. If it does not turn freely, the compressor may need to be replaced.
Additional Test: Use a multimeter to check the voltage at the compressor connector when the A/C is on. If there is no voltage, the problem is upstream (e.g. relay or wiring).
6. Check the internal thermostat
- Problem: A faulty temperature sensor or thermostat can prevent the air conditioning from turning on.
- Solution: Use a multimeter to check the thermostat for continuity. If it doesn't work, consider replacing it.
Tip: Also check your air conditioning settings to make sure the problem isn't related to the control panel.
Conclusion
Before considering an expensive overhaul of your entire system, follow these steps to find the cause of your air conditioner malfunction. Components such as the pressure switch, relay, or wiring can be repaired or replaced at a low cost.
If you are not confident in diagnosing or repairing the problem yourself, hire a professional to avoid further damage. An accurate diagnosis could save you hundreds of dollars and restore your air conditioner to full efficiency.
