Most problems with a car's air conditioning develop over time, so if you have this system checked and maintained as needed, the air conditioner may actually last for as long as you own your vehicle. However, if the vehicle's air conditioning does fail to cool the interior of your car or truck, you might note some troubleshooting tips that can help you pinpoint what's gone wrong, and what needs fixing. 

Moisture

Moisture traps and holds heat, which is why your home's air conditioner may have a dehumidifier attached to it. If moisture in the home is not removed, that air conditioner won't be able to cool the home's interior, no matter how long it runs. Your car's air conditioner won't usually have a dehumidifier attached to it, but if it should get moisture trapped inside any of its components, this will mean that it simply fails to cool the vehicle, as that moisture will keep heat trapped inside the vehicle. An air conditioner repair person can find the cause of this built-up moisture, dry out and clean the unit, and ensure it's operating as it should.

Bad smell

If you notice a pungent odour coming from the dashboard vents, this often means that mould, mildew, bacteria, and fungi are collecting inside the air conditioning unit. These irritants then get blown into the cab of the car when you turn on the dashboard fan, creating that smell; like moisture, these irritants also trap heat in the vehicle and keep the air conditioner from working. If you notice these bad odours when the air conditioner fails, be sure to note this to your repair person so they can properly clean the unit will also ensuring it cools the vehicle.

Compressor

Air conditioning coolant needs to be compressed to become cold. Your vehicle's air conditioner is then outfitted with a small compressor that compresses that coolant as it circulates around the unit. If the compressor is cracked or split, or if there is a build of debris, dirt or rust around the compressor, it may not work as it should. In turn, your vehicle may have enough coolant, but that fluid doesn't actually become cool!

In some cases, the compressor can be flushed out, just like the car's radiator, to remove debris, rust and other sediment. If it's cracked or otherwise damaged, however, it may simply need replacing for the car's air conditioner to be functional again.