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Car AC System Failure: Top 7 Reasons Why This Happens

The Car AC system

This feature in your car 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 car, in fact, it’s a necessity. The AC is your escape from the prickling heat and humidity.

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 AC system fails.

GoMechanic: Your Car AC Expert


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

Top Reasons for Car AC failure

  • 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 lack of refrigerant, a clogged expansion tube or refrigerant charging hose, 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.

  • 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.

  • Foul odor 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, moldy smell.

Reason: Your HVAC (Heating Ventilation Air Conditioning) filter or 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.

Bad odors may also be caused by moldy evaporator case or air vent. This can put your health at risk because mold can cause an allergic reaction to some people. Regular cleaning of the evaporator case and the air vent will help fix this issue.

  • 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.

GoMechanic: Your Trusted Car AC Expert

  • 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 which 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.

  • Burning Odour 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 electricals issues.

  • 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.

GoMechanic: Your Car AC Expert

 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-up 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.

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