Car air con not working? 7 causes and what you can check yourself

Not every air con that blows warm air is faulty. Sometimes the cause is in the controls or the ventilation. So check these four points first. It will take you a few minutes.

Have you checked these points and is the air still warm? Then it is probably one of the seven causes below.

The most common cause is too little refrigerant. The refrigerant is the gas that circulates in a closed circuit and carries the heat out of the car. A fault can have more than one cause. The descriptions below give a first indication. They do not replace a measurement.

1. Too little refrigerant through slow loss
An air con system is sealed. Even so, refrigerant slowly escapes through the hoses and seals. According to the ANWB, the Dutch motoring organisation, refrigerant needs topping up every 4 to 6 years on average. First the air becomes less cold. If there is far too little refrigerant, the pressure sensor switches the compressor off to protect it. The air con then blows warm air.
Solution: an air con service. We extract the refrigerant, vacuum the system, check that it is sealed and refill it to the factory specification. Read more about an air con regas.

2. A leak in the system
Does the air con blow warm again within a few months of being refilled? Then there is probably a leak. Common leak points are the O-rings at the connections, the condenser, the hoses and the service valves. The European directive on car air con systems (2006/40/EC) states that a garage must not refill a system that has lost an abnormal amount of refrigerant until the repair has been completed. So we do not refill a system that we know is leaking.
Solution: a leak test with nitrogen, followed by repairing the leak.

3. A faulty air con compressor
The compressor pumps the refrigerant around and pressurises it. Without a working compressor the air con does not cool. A worn compressor often makes a ticking or rattling noise when you switch the air con on. Sometimes it no longer engages at all. A noise alone is not a diagnosis: squealing, for example, more often comes from the auxiliary drive belt or a tensioner pulley.
Solution: replacing the compressor. This is one of the most expensive air con repairs. That is why we first measure whether the compressor really is the cause. You can read more on our page about replacing the air con compressor.

4. A dirty or leaking condenser
The condenser sits at the front of the car, usually behind the grille and in front of the radiator. It releases the heat from the refrigerant into the outside air. If it is clogged with leaves and insects, or damaged by stone chips, it does this less well. The air con then cools poorly, especially when the car is stationary and in traffic jams. A faulty cooling fan causes the same complaint.
Solution: cleaning the fins or, if there is a leak or damage, replacing the condenser. We also check the cooling fan. Read more about replacing the air con condenser.

5. A faulty magnetic clutch
On many belt-driven compressors, a magnetic clutch switches the compressor on and off. If the clutch does not work, the compressor does not turn, even if the rest of the system is in order. You then often hear no click when you switch the air con on. That alone does not prove the clutch is faulty. Many newer compressors and electric compressors have no magnetic clutch. Then you will not hear a click either.
Solution: on many compressors the clutch can be replaced separately. On others the whole compressor is replaced.

6. A faulty blower fan or blower control
The blower fan is the fan behind the dashboard that blows air through the vents. If it is faulty, little or no air comes out of the vents, even on the highest setting. Sometimes the blower motor hums or squeaks. Does the blower only work on the highest setting? Then the blower resistor is often faulty. On an automatic climate control system, this part is called the blower control module. A clogged cabin filter also lets little air through.
Solution: checking the filter and replacing the blower fan or the control module. How much work that is varies a lot between models.

7. An electrical fault or a blown fuse
Sometimes the cause is a fuse, a relay, a pressure sensor, the wiring or the controls. According to the ANWB, broken wiring or a blown fuse is a repair that is not expensive. On newer cars, the car usually stores a fault code when something goes wrong. A fault code is a pointer and not necessarily the cause. That is why we carry on measuring after reading it.
Solution: reading the fault codes, measuring and repairing the faulty part.

What you notice often says a lot about the cause. Use the table as a first indication. It is not a diagnosis.

First indication based on the complaint. The cause only becomes clear from a measurement.

The cost depends on the cause. An air con service is a small expense, a new compressor or evaporator a large one. That is why the diagnosis is the first step. You hear in advance what the diagnosis costs. After that you receive a quote listing the parts, the labour, the refrigerant and the VAT. We only carry out repairs once you have agreed.

Amounts marked “according to the ANWB” are market indications from the ANWB and not a quote from us. Our air con service includes extracting the refrigerant, vacuuming, the leak-tightness check, refilling to the factory specification and VAT.

Have you already had a quote elsewhere, for example for a new compressor, and would you like to be sure first that it is needed? Then you can have a second opinion with us. It costs € 145, including up to one hour of investigation.

You can do four checks yourself, without tools. They help you tell us more clearly on the phone what you have noticed. Repairs and refills belong at the garage.

1. Listen when you switch the air con on. Do this outdoors. Put the car in P or in neutral, with the handbrake on. Leave the engine running and switch the air con on. Listen for a click, ticking or rattling. Keep your hands, clothing and hair away from belts and fans.
2. Look at the condenser. Look through the grille at the visible part. Are there a lot of leaves, dirt or insects in front of it? Then have the condenser cleaned. Do not use a pressure washer at close range, because the fins bend easily.
3. Feel how cold the air gets. Set the air con to the coldest setting and leave it on for a few minutes. If the air hardly gets colder than the outside air, a measurement is needed.
4. Check the cabin filter. A clogged filter lets little air through. The owner’s manual shows where the filter is and when it needs replacing. On many cars it sits behind the glovebox. Is the filter hard to reach? Then let us check it for you.

Better not to do yourself: refilling with a DIY recharge kit from a shop. According to the ANWB, refilling it yourself is not permitted and must be done by a certified company, because the system is under pressure. With a recharge kit you also do not know how much refrigerant is still in the system, and a leak stays where it is. Too much refrigerant is bad for the compressor. Some kits contain a leak sealant that can contaminate the system and the workshop equipment.

A diagnosis is needed as soon as the air con still does not cool after the checks above, or if you recognise one of the signs below. Finding the cause reliably requires measuring equipment: an air con service station that measures the pressures and diagnostic equipment that reads the fault codes.

Do you drive an electric car or a plug-in hybrid? On many electric cars and plug-in hybrids, the air con system also cools the battery. If the air con is not working properly, the car may limit rapid charging or power to protect the battery. So do not wait too long. Read more about the air con in an electric car. Our mechanics hold the GMTO certificate (the Dutch qualification for working on high-voltage systems) for work on hybrid and electric cars.

We work in a set order: measure first, and only then refill or replace. That way we reduce the chance of a part being replaced unnecessarily. Our mechanics are F-gas certified for car air con systems with R134a and R1234yf.

1. Call us with your registration number. Tell us what you have noticed. Has the air con been refilled before? Please mention it. Then we start with the leak test and not with refilling. You hear in advance what the diagnosis costs.
2. Measuring the pressures and reading the fault codes. We connect the air con service station and measure the high and low pressure. These pressures show whether there is too little refrigerant, whether the compressor pumps properly and whether the condenser can get rid of its heat. We read the fault codes with the diagnostic equipment.
3. A leak test if we suspect a leak. We extract the refrigerant and pressurise the system with dry nitrogen. If the pressure drops, we look for the location of the leak.
4. Quote and your approval. We tell you what we have found and you receive a quote for the repair in advance. We only start once you have agreed. If more work turns out to be needed along the way, we discuss it with you first.

A complete air con service takes about 45 minutes to an hour and you can wait for it. A leak test or a larger repair takes longer and depends on the car and the delivery time of the parts. We work by appointment, Monday to Friday from 8.00 to 17.30 and on Saturday from 9.00 to 15.00. For a quick question or check you can walk in without an appointment. You can read all about the air con service and our prices on the page car air conditioning.

According to the ANWB, refrigerant needs topping up every 4 to 6 years on average. So refilling every year is not necessary. According to the ANWB, it is sensible to have the air con checked every year, for example during the service. Check your car’s service schedule too. How to read it is explained in your car’s service schedule explained.

Do not wait for the average if the air con starts cooling less well sooner. In that case there is already too little refrigerant. If the air con is empty again within a year of being refilled, there is more going on than normal loss and we look for the leak first.

The best protection is to use the air con regularly all year round and have it checked in good time. The refrigerant carries oil that lubricates the compressor. According to the ANWB, switching the air con on now and then helps prevent damage. If the air con is off for a long time, refrigerant slowly leaks away, according to the ANWB.

Usually there is too little refrigerant in the system, through slow loss over the years or through a leak. Other causes are a faulty compressor, a dirty condenser, a faulty magnetic clutch and an electrical fault. Which one it is only becomes clear from measuring the pressures.

You hear in advance what the diagnosis costs when you call with your registration number. According to the ANWB, an air con check costs a few tens of euros, but nothing is refilled. After the diagnosis you receive a quote for the repair. We only carry out repairs once you have agreed.

That depends on the car and the complaint. Measuring the pressures and reading the fault codes is often quick. If a leak test is needed as well, it takes longer. You hear in advance what the diagnosis involves and roughly how long we need.

Then there is probably a leak and refilling again will only help for a short time. Under the European directive on car air con systems, a system with an abnormal leak is only refilled once the repair has been completed. Mention it when you call. Then we start with a leak test using nitrogen and not with refilling.

While you drive, the airflow passes through the condenser. When the car is stationary, the cooling fan has to do that job. If the air con cools poorly in traffic jams and well on the motorway, the condenser is often dirty or the cooling fan is not working. Too little refrigerant can also cause this complaint.

Yes. Sometimes an air con works again after a while, for example because of a sensor or relay that fails now and then, or a safety function that switches the compressor off temporarily. The cause has not gone away. Have the air con checked if it keeps cutting out.

No. According to the ANWB, refilling it yourself is not permitted and a certified company should do it. With a recharge kit you also do not know how much refrigerant is still in the system, and too much is bad for the compressor. A leak also stays where it is.

If the air con is off for a long time, refrigerant slowly leaks away, according to the ANWB. In spring there is then too little left to cool properly. An air con service is often enough. If the air con is empty again within a season, there is a leak. So switch the air con on regularly for a while all year round.

Yes. For the engine that is usually not a problem, but it depends on the cause. A compressor that seizes can make the auxiliary drive belt slip or break. So switch the air con off if you hear rattling. On an electric car, a poorly working air con can limit rapid charging.

• ANWB: De airco van mijn auto werkt niet goed: wat nu? (in Dutch)
• ANWB: Airco onderhoud: dit moet je weten (in Dutch)
• EUR-Lex: Directive 2006/40/EC relating to emissions from air-conditioning systems in motor vehicles (Article 6(3))
• ANWB: Interieurfilter vervangen: zo doe je dat (in Dutch)