How to Fix Your Car’s Air Conditioner

Come the height of summer, effective temperature control is no longer just a luxury, but a necessity. Here’s a brief overview of how AC (Air Conditioning) works, or why it might not be working, as well as possible measures that one could take to fix it. Essentially, AC is a refrigerator unit. It would be impossible to describe every single model in this article, so for simplification purposes, all that an AC unit does is to relocate heat from the inside to the outside of the car using a compressed refrigerant. 

Photo Credit: Designlazy.com

Steps

1- Familiarise yourself with the various components:  The compressor pressurizes and circulates the refrigerant which carries the heat, the condenser allows the escape of heat from out of the car by changing the phase of the refrigerant gas to liquid, the expansion valve drops the pressure of the liquid, the evaporator transfers the heat to the refrigerant from the air blown across it, and the dryer/receiver filters the air before delivering it into the car. 

2- Understand the air conditioning process. Firstly the refrigerant is condensed (the process of pressurizing the refrigerant causes it to loose heat to the air which then escapes out of the car) changing the refrigerant’s state from a gas to a liquid. The compressed refrigerant then passes into the expansion valve and evaporator whereby its change of state back to a gas causes it to heat up and so ‘sucking’ heat out of the air. This air is then passed through the dryer/receiver to the inside of your car. The cycle is then repeated over and over. 

3- To begin to evaluate the problem, firstly check for leaks around the ‘circuit’. Leaks will cause the refrigerant to loose pressure in the system, rendering it ineffective. Although leaks are easy to spot, they require lots of adjustments and dismantling to fix. Do not interfere with the valves as this is illegal and releases harmful gases into the atmosphere. 

4- Check that the compressor is working. Turn on the engine and the AC and look for a pump like object with rubber and steel connections. Your car should have a manual that will help you locate the AC unit. It should have a valve or 2 that resembles those that you find on a bicycle wheel. The pulley on the side of the compressor should be turning. If this is not the case then the compressor’s clutch is not engaged. This will either be due to electrics or low levels of refrigerant. Also check that the compressor seal is still intact. 

5- Check general electrics, switches, fuses around the system, or look for a broken fan belt.

6- Check for any cooling as you may just be low on refrigerant. If there is minimal cooling of the air then the system could still be working but just have a lower pressure of refrigerant. Use a refill kit to top up the system but be sure not to overfill as this could actually decrease performance.  

Tips

To check whether the compressor clutch is broken or if it is simply a case of bad wiring, find the connector in the middle of the wire leading from the compressor to the clutch and unplug it. Using a length of wire, connect this to the plus side of your battery. Should you here a kick, the electric clutch is still working and you should then check the wiring throughout. 

Occasionally, especially with older cars, the problem lies with excess heat coming off of the engine which decreases the performance of the AC system. If this is the case, you can insulate the cold AC pipe to minimise this effect. 

If you have any reason to suspect that your refrigerant has leaked out completely then it would be better to call in a professional.

Do not touch liquid refrigerant because as it evaporates it could freeze burn your skin.

Do not connect refrigerant cans or leak-detectors to the high pressure side of the AC circuit. This side is usually marked with “high” or “H”. Cans could explode in this circumstance. 

Venting of refrigerants is illegal in most countries. Do not do it!