Why Is My Car Air Con Not Blowing Cold?

How your air con actually works

Your car air con works a lot like a fridge. A pump called the compressor pushes a special gas, called refrigerant, around a sealed loop of pipes. As the gas changes from liquid to vapour inside the dashboard, it soaks up heat, and the fan blows that cooled air into the cabin.

Because it is a sealed system, nothing should normally be used up. When the air stops coming out cold, something has changed: the gas has escaped, a part has stopped working, or the air is not getting through properly.

Low gas is the most common cause

Even a healthy system loses a little refrigerant each year through the seals and hoses. Over a few years the level drops far enough that the air con only cools a little, then not at all.

If your air con has faded slowly over a couple of summers, low gas is the likely cause and a re-gas often brings it back. If it went warm quickly, or went warm again soon after a re-gas, there is usually a leak that needs finding first, otherwise the new gas will simply escape again.

Cars built in recent years use a newer type of refrigerant to older cars, and the two are not swapped. We check which one your car takes before we start.

Leaks, damaged condensers and failing compressors

The condenser sits right at the front of the car, in front of the radiator, so it takes stones and road grit. Over time it can be holed or corroded and start to leak. Pipes, seals and valves can leak too, often leaving a thin oily film where the gas has been getting out.

The compressor is driven by the engine belt and has a clutch that switches it on and off. If the clutch does not engage, or the compressor itself is worn, the system cannot move the gas around. A noisy whine or rattle when the air con is switched on can be a sign of a compressor on its way out.

There are electrical causes as well. A blown fuse, a faulty relay or a pressure sensor giving a false reading can stop the compressor running, even when there is plenty of gas in the system.

When the air is weak or smells musty

Sometimes the air is cold but there is not much of it. A blocked cabin filter, also called a pollen filter, is a common reason. It cleans the air coming into the car and gradually clogs with dust and leaves. It is usually changed as part of a service.

A musty or damp smell when you first switch on often comes from moisture and bacteria building up around the part behind the dashboard that does the cooling. If the air is cold on one side and warm on the other, a flap inside the heater box may be sticking.

Simple habits that keep it working

The best thing you can do is use your air con regularly, even in winter. Running it for ten minutes or so every week keeps oil moving around the seals so they do not dry out. It also clears a misty windscreen much faster than the heater on its own.

Keep an eye on the grille at the front of the car too. Leaves and debris packed against the condenser can stop it getting rid of heat properly, which makes the whole system work harder.

Get it checked in Pelsall

When your car comes in, we check the pressures, look for leaks and make sure the compressor and fans are doing their job, so we fix the cause and not just top it up. Mark has been working on cars for more than 30 years and air con is one of the jobs we do every week.

Call us on 01922 682200 or book online. We will tell you what we find and give you a clear quote before any work starts, so you can drive around Walsall cool and comfortable this summer.