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Car AC System Failure: Top 7 Reasons Why This Happens

The Car AC System

This feature in your car is responsible for a relaxed and comfortable drive. Although one can drive without it, we can only imagine all the sweating and discomfort in the cabin. It is now a standard feature across all cars, in fact, it’s a necessity. The AC is your escape from the prickling heat and humidity.

Hyundai Grand i10 AC Vent

But, not everything works as it should and all the time, does it? The AC system in your car is also prone to failure and breakdowns. In this blog post, GoMechanic shows you, Top 10 reasons why your car’s AC system fails.

There can be a myriad of issues when it comes to the AC system owing to complex mechanicals as well as electrical problems, like a failed O-ring seal causing a FREON leak or a clogged expansion tube or just a faulty compressor.

Top Reasons for Car AC failure

  1. Poor Airflow

    Upon cranking up the AC, if you notice a weak airflow from the blowers and no or low cooling, this is the most visible sign that your AC needs repairs.

    Reason: it may be due to a lack of refrigerant, a clogged expansion tube or refrigerant charging hose, a broken compressor, broken blower motor, damaged condenser or evaporator, or a failed fuse or switch. This symptom may need small maintenance or a major repair, depending on what’s causing it.

  2. Loud Noise while the AC is on

    Loud noises when the AC is switched on is another potential symptom of a failing AC.

    Reason: A Faulty AC Compressor. Much like other accessories driven by the engine’s belts, the AC compressor has several interior components and uses a sealed bearing to turn. If any of the interior parts break, or the compressor’s internal bearings fail or seize, then all sorts of noises can be produced as a result.

  3. Foul odour in the cabin

    This is probably one of the most repulsive things ever caused by a failed AC. When you enter your car and get a whiff of musty, pungent, mouldy smell.

    Reason: Your HVAC (Heating Ventilation Air Conditioning) filter or the cabin air filter may be dirty or worn. You need to have this cleaned, or perhaps a replacement is necessary. Regular changing of air cabin filters will help prevent long-term damage to your air conditioning system, and it will also help reduce your fuel consumption.

  4. Bad odours

    may also be caused by a mouldy evaporator case or air vent. This can put your health at risk because mould can cause an allergic reaction in some people. Regular cleaning of the evaporator case and the air vent will help fix this issue.

  5. Water inside the cabin

    When you park your car after a drive with the AC on, you would have observed, a puddle of water underneath the car. That’s normal and in fact, a sign of a completely healthy AC system. But when you see water inside the cabin, that is when the trouble begins.

    Reason: The condensed water from the evaporator needs to drain out, but due to a clogged drain hose, it seeps into the cabin. It is advised to get the car to a garage as soon as possible as water inside can cause significant damage to the vehicle’s electrical system and can even pose a shock hazard.

  6. AC starts to cool; then it suddenly gets warm

    This is the most common complaint we’ve heard from our customer who comes in for AC repairs. When you turn on the AC, it’s all well for a few minutes after which, you start feeling warm air blowing from the vents.

    Reason: It may be caused by a clogged expansion valve that blocks the refrigerant from flowing into the evaporator. This may also be a cause of a damaged compressor clutch that prevents the compressor to maintain the correct pressure. Or it may also be a sign of a blown fuse or leaks.

  7. Burning Smell from the AC

    When you switch on the AC, you get a sharp burning smell.

    Reason: Chances are the wirings of your compressor are burnt or overheated. Damaged compressor wirings prevent the vehicle’s air conditioning system from functioning properly. This will need a complete wiring replacement immediately to avoid electrical issues.

  8. You switch on the AC, and nothing happens
    You press the AC button, the blower throws air, but not cold air.Reason: The compressor clutch is not moving. The clutch on the compressor is what allows the pulley to engage and disengage from engine power so that the compressor is only turning when it needs to be. The clutch can seize, which permanently keeps the compressor activated; or it can break, which means the compressor will not be able to receive engine power.

The Compressor: Heart of your AC

The AC compressor is one of the most critical components of a vehicle’s air conditioning system. It is responsible for pressurising the AC system and keeping the refrigerant flowing so that it can function properly. Because it operates in a continuous cycle on and off, it is subject to wear every time the AC is turned on. Just like any other component on a vehicle, it will eventually fail and need to be replaced. The compressor is responsible for pressurising and distributing the refrigerant. If there is any problem with the compressor, the rest of the AC system will be affected.

The air conditioning system is an essential component of your vehicle that makes your ride more comfortable. Getting a regular car maintenance check-up is vital to keep your A/C system in its best condition and to prevent long-term and more severe damage. Maintenance and thorough check-ups of your A/C system should ideally be done at least once a year. After all, prevention is better than cure.

The air-conditioning unit in a vehicle has three parts. It has a compressor, a condenser, and an evaporator. For the unit to function smoothly, each of these parts must be regularly serviced and maintained.

Akshat Ajeya
Akshat Ajeya
Lead, Content & Creatives at GoMechanic | Automobile Scale Model Collector | DIY guy | Consumer of many foods | CVT is not that bad


  1. It’s interesting to know that hearing a loud noise when your AC is on will be a sign that you need to repair it. My husband bought a pickup truck recently, and we are looking for advice about what to do. I will let him know about your recommendations to choose the right professional to help him.

  2. It caught my attention when you said that after a car sits with the ca on after a drive, it will lead to leaving water in the cabin. My brother was cleaning his car the other day and noticed a paddle f weather stains on the rugs and carpet of the car. I will let him know that it could have been the reason why his AC stopped working and the reason for the water stains.

  3. Hi, I am facing very strange problem with my Baleno 2016. Driver side vent is blowing cold air, while rest of the 3 vents are giving ambient air. What can be the reason ?

    • Hi Sanket,
      We suspect that there is an issue with the cooling coil of the air-con system of your car. You can get it checked and repaired from GoMechanic. All you have to do is download the app and a properly working AC is just a few clicks away. You can also book the AC service on the website:
      Stay tuned!

  4. My ciaz AC was not working. went to dealer. He says , sensor on compressor is not working and they bypassed the sensor. directly connected to compressor. Now AC is working. Is there any future problem?

    • Hi Sanjaya,
      There is no specific space or measurement between the radiator and condenser. But it also should not hamper the installation of either the bumper or the radiator/condenser fan. Hope it helps.

  5. My car AC turns on when I start at first in morning and once i make a stop, switch off the engine and start again, the AC does not turn on. none of the AC lights will be on. But if the leave the Engine off for the whole day and then turn on Engine in evening, the AC turns on and works well. excellent cooling. There is no refregenrant leak nor the coolant leak. What might be the problem?

    • Hi Prashanth
      To diagnose the exact issue, we would require to physically inspect your car once. Request you to drop your contact number so that our service experts can call you back and schedule an appointment for the same

  6. Hi I have a 2013 honda odyssey exl. AC has never had any problems, always bern cold, never had any leakage, however, one day after hitting a large pothole on the side of the compressor, the vehicle begins to stall, basically moving slowly forward and back. Anyway I tow to my house, file a claim, and immediately get an ins adjuster show up. Has me turn on the veh go in rev and forward, suddenly hes yelling, shut the veh off. We smell and see smoke coming from the engine pulley area down below towards the compressor.

    My question is, being that my AC was serviced regularly and in good running condition. What could have caused it to suddenly fail and burn? Could the pothole have somehow caused its failure, i mean the mechanic didnt see much damage to any AC components, but could damage to other vehicle components relate to the AC compressors’ sudden failure? Any intel would be great. Thanks.

    • Hi Rosaline
      Honestly, it is not possible to diagnose your issue without a proper physical inspection. However, I request you to take your car to the authorised service centre as you seem to be from outside India, and we are serviceable only in India yet.

  7. While AC is switched on in my alto k10, I felt smell of patrol. What could be the reason of this defect and what are the adverse affects? Please explain.

    • Smelling fuel while the car is running is a bad sign and we strongly suggest you stop driving your car and get it checked at a nearest car workshop.

  8. I am facing problem in AC in my Hyundai Verna 2011 model. Whenever the car is standing with engine turned on, the AC becomes less effective slowly with no cooling after few minutes. As soon as the car starts to travel the cooling starts again. If the car is continuously running then the cooling is fine but when it stops then slowly cooling becomes less effective. Can you let me know the reason.

  9. Hello there,

    About few weeks ago, I noticed leakages around the hose with the discharge pipe of my ac. I had a technician change. And while reassembling it, flushed the compressor using some.reverse engineering technique. A test run on the spot at the garage had the ac cooling okay.but the next day after getting back on the road proper, I realised, one minute my AC is cooling okay and the next is just a mixture of warm air.

    Same guy (technician) is saying my thermostat is bad. And to God I hope he’s wrong. Hence my reason for coming inboard here.

    Thank you all for your response in advance

  10. I have a 2010 Mercedes Benz E 350 4matic. AC blows warm on start up if the car sits for a few days. After shutting engine off AC works fine. Is this a compressor clutch or expansion valve problem??

  11. I have taken my 2019 ford expedition in 3 separate times to get my ac fixed with ford. All three times the rear blows warm then the front gets warm. First time they said no leak filled with freon. Second time they said now there’s a Crack in the evaporator core. Now we bring it in for the 3rd time and now they said it’s a compressor leaking. What can I do. They are now trying to charge me another 1900$. It’s been almost 4000$ to get my ac fixed.

  12. I changed the complete AC system (Condenser, Compressor, Evaporator and the valve) of my Mercedes C230 2005 model. After 4 months, I realised the AC was blowing hot air again. I made a technician inspect it and I was told the system has become black and I needed to replace all the parts again. You know this replacement doesn’t come cheap. I will like to know what might have caused that before I make any attempt to fix it again.

    • Hi Sherm
      This will be possible only after a physical inspection of the car as we will be able to figure the exact issue out after that only. Request you to droop your contact number for us to call you back and arrange things for you.

    • While we do not promote rash driving in any scenario, it is true that an overheated engine can cause a serious issue to your vehicle, including the AC pipes and other systems.

  13. I have a 2006 Suzuki swift and I had it re gas and check for leaks but they cant find a leak in the system but after 2 days after the re gas it goes hot what could be causing this thanks

  14. While driving (especially when it’s hot, like in the afternoon) our ac suddenly stops blowing air or totaly stops working and we don’t know why… give it an hour it will work again.

    Note: new condenser and new evaporator.. filter is also new.. freon is also ok.. no leaks or so


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