What to do if the inside of your car won't cool down - image of a woman drinking bottled water in a car

Help! The inside of my car won’t cool down

British summer is notoriously unpredictable, but from time to time we have a proper heatwave. We’ve all been there: it’s a scorching day, you get into your car, crank up the air conditioning (AC), and… nothing. Instead of a refreshing blast of cold air, you’re met with a disappointing trickle of warm air.

What to do if the interior of your car won’t cool down

So what do you do if the inside of your car starts won’t cool down? Here’s a breakdown of some common reasons why your car’s AC might not be working and what you can do about it.

1. The AC is low on refrigerant

Refrigerant is a special fluid in your car’s AC system that helps cool the air. It absorbs heat from the inside of your car and releases it outside, allowing cool air to circulate inside.

For the scientists: refrigerant is a liquid with a very low boiling point. Air conditioning works by pressurising the refrigerant which makes it extremely cold. This is how it cools down the air in your car quickly.

How do I know if my aircon is low on refrigerant?

If your AC is blowing warm air, it could be a sign that the refrigerant is low.

There is no way of checking your aircon refrigerant levels yourself. The refrigerant is contained in a sealed, pressurised system. You’ll know if your system has low or no refrigerant because it will automatically shut down.

Is it serious?

Not really, unless you’re particularly heat sensitive! Low gas just stops the aircon from working.

You’ll need to get your car to a mechanic to have the refrigerant level checked and, if necessary, refilled. The mechanic will also check for leaks in the system and repair them.

2. The cooling fan is faulty

The cooling fan that cools your car’s engine also cools the refrigerant used by your air conditioning system. The cooling fan will run continuously when the air con is switched on to stop the inside of your car overheating.

The cooling fan helps move air over the condenser, which releases the heat absorbed by the refrigerant. This process is essential for maintaining cool air inside your car.

How do I know if the cooling fan it faulty?

This should be evident quite quickly. If the AC is only blowing warm air when your car is stationary or moving slowly, but cools down once you start driving, the cooling fan might be the issue. You might also hear strange noises coming from the fan area.

Is it serious?

Yes, a faulty cooling fan can prevent your AC from working properly and can also lead to overheating issues with your engine. If you notice that the cooling fan is not working with the air con on then you should get it checked out as soon as possible.

Bring your car to a workshop you trust and get a motor engineer to inspect the cooling fan. The cooling fan may need to be repaired or replaced to get your AC back to working order.

3. There is a pressure sensor error

The pressure sensor monitors the pressure of the refrigerant in the AC system. It ensures the pressure is within safe limits, which is crucial for the system to function correctly. If the sensor detects that the pressure is low, it will automatically turn off your car’s aircon.

How do I know if there’s a pressure sensor error?

Keeping the air conditioning system at the correct pressure is an important safety feature. So if there is any kind of fault with the pressure sensor, it may turn off the air con when everything else is ok.

If there’s a pressure sensor issue the AC might shut off intermittently. A diagnostic tool can confirm this error.

Is it serious?

While not immediately damaging, a pressure sensor error can prevent your AC from working correctly and may lead to other issues if ignored.

Visit a mechanic to have the sensor checked. They may need to recalibrate, repair, or replace the sensor.

4. Compressor failure

The compressor is the heart of your car’s AC system. It pressurises the refrigerant and circulates it through the system, facilitating the cooling process.

How do I know if the compressor has failed?

If you hear loud noises when the AC is running, or if the AC stops blowing cold air entirely, the compressor might be the culprit.

Is it serious?

Yes, a failed compressor can bring your entire AC system to a halt. It’s also one of the more costly components to repair or replace.

You’ll need to visit a mechanic to diagnose the issue. If the compressor has failed, it will likely need to be replaced. This is a more complex and expensive repair, but necessary for restoring your AC.

Keep your car cool with a regular air conditioning service

If you think you might have a problem with your air conditioning you’re going to need it looked at by a trained professional. Working on a car’s air conditioning system can be very dangerous because of the high pressure gas and the very cold temperatures.

Two of our engineers are qualified to work on vehicle air conditioning. David and Luka would be happy to check your car’s aircon for faults and service the system to keep you cool as the temperature rises.

Give us a call on 0116 3190 118 or mobile 07850 881 911. You can also get in touch via our contact form. Alternatively, if you’re in the area feel free to drop in to our friendly garage at on Shaftsbury Road, Leicester, LE3 0QN.

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