What’s wrong with my car’s AC?

This article will cover the major symptoms that arise as a result of problems with your car’s air-conditioning system, their actual causes and how you can get them fixed.

With the onset of the summer, it’s time we ensure that our cars’ AC is functioning properly. Listed below are the various symptoms which will tell you that your car’s AC is malfunctioning which would warrant an immediate checkup and rectification. We have also mentioned what needs to be done to rectify the issue. In most cases it is recommended that you take the help of an A/C technician to do the work.

1. My Car AC is not cooling effectively — The ideal temperature inside the car’s cabin should be between 8–12 deg C when the ambient temperature is between 28–40 deg C (which is mostly the case in India). Loss of cooling ability can be credited to a variety of faults within the AC system the most frequent ones which are covered below –
2. AC Gas / Refrigerant Leakage — Leakages usually happen at the connection points of AC pipes/hoses and other components of the AC system. Leakage of refrigerant gas reduces cooling power of the car’s aircon. In some cases, the refrigerant leakages can be detected by visual inspection of liquid refrigerant accumulation near ac hoses inside the engine bay. If the leakage is caused by broken seals or cracked hoses, a replacement of the damaged part is in order.
3. Radiator fan malfunction — The main function of the radiator fan is to dispel heat from the aircon system to the atmosphere. If the radiator fan fails, the refrigerant continues to be in gaseous state thereby not being able to absorb more heat from the inside of the car/cabin which results in reduced cooling power. This will cause excessive heat build up inside the system over time, causing gas to escape and refrigerant pressure to drop.
4. The bonnet is popped up, the engine is cranked and the radiator fan is visually inspected. If the fan does not rotate when the AC is switched on, it means it damaged and will require replacement.
5. In some cases, the resistor connecting the radiator fan to the A/C’s electric circuit tends to get damaged over time. They usually last around 50k km for most vehicles. If this component fails, it will cause the fan to malfunction. If this is confirmed as the problem, the resistor needs to be replaced immediately.
6. AC Gas Low — If there is less pressure of AC Gas within the system, the cooling power of the AC will also reduce. This can be determined with the help of the AC pressure Gauge. Depending on the existing pressure, top up the gas or recharge it completely to get the desired effect of your A/C.

• Cooling Coil damaged — If there is any leakage present in the cooling coil, it will lead to loss of cooling power of the ac. Leakages occur due to damages sustained by the cooling coil as a result of rash driving. In some vehicles, the cooling coil is easily accessible but in others, it’s an arduous task.

1. Once the cooling coil is removed, it needs to be cleaned and checked for leakages. If there are damages on the body of the cooling coil, a replacement is in order.

• Blocked or Choked Cooling/Evaporator coil –
• Cooling coil is subject to build up of sludge and contaminants over a period of time from multiple sources, not to mention moisture that is retained within the system. This restricts the flow of refrigerant thereby affecting the cooling power of the car. It is recommended to use an AC flush which can flush out the build up and contaminants inside the evaporator coil thereby improving the flow of refrigerant inside it. In order to flush the coil it will need to be removed from its place.
• The cooling coil also tends to get covered with dust. This reduces its conductivity which means less heat will be absorbed from inside the cabin. To address this issue the cooling coil will need to be removed from the car, cleaned and put back in place.
• Frozen evaporator or cooling coil — a frozen evaporator coil will mean less cooling power of the ac since refrigerant is not cycled properly within the system. It can be caused due to the following reasons –

1. Faulty thermostat — if the thermostat stops working, it will not tell the compressor when the cabin is too cold, hence, the operating temperature of the system will drop significantly causing the refrigerant in the cooling coil to freeze over. Thermostat will need to be replaced in this situation.
2. If the thermostat is not set correctly, it will need to be calibrated and reset.
3. Compressor malfunction/failure — compressor malfunction can be caused due to the following reasons.
4. Broken drive belt. Replace the drive belt immediately.
5. Broken clutch wire or no 12V power — check for wiring issues
6. Faulty Compressors will usually need replacement and cannot be overhauled easily
7. Low refrigerant — low pressure in the system will cause the pressure switch to cut off clutch power. Recharge refrigerant.

• Drive belt slippage — the AC compressor is driven by the rotation of the engine’s crankshaft. The drive from the crankshaft is transferred to the compressor by means of a tension belt. If this belt is worn out or loose it will cause belt slippage and malfunction of A/C compressor. In this case, the belt will need to be replaced or tighetened.

1. Plugged receiver/dryer — this component is responsible for dehumidifying the air entering the cabin. If this faulty, it will cause more moisture to build up within the system thereby reducing cooling power. In this case, the receiver/dryer will need to be replaced.
2. Expansion valve broken/defective — the expansion valve is responsible for reducing the pressure of the refrigerant when it’s in the liquid phase. This low pressure liquid flows through the evaporator coil which absorbs the heat from inside the car, converting the refrigerant from liquid to gas. If this valve is broken, it needs to be replaced to ensure proper functioning of AC

• There is reduced airflow from the AC vent –

1. Choked AC (or “Cabin”) Filter — Airflow through the AC vents will reduce when the cabin filter or AC filter is clogged. This filter is responsible for filtering the air inside the car’s cabin. Clogging occurs if the filter has not been cleaned for a long period of time. If the air filter is not excessively clogged, it can be cleaned and placed back in its housing. Otherwise, it will need to be replaced (usually every 15000–20000 km and also depending on the ambient air quality).
2. Blower Motor Malfunction — The blower motor is responsible for forcing cool air into the cabin. Chances of blower motor failure is extremely rare. Symptom of blower motor failure is a whistling or sharp sound from behind the dashboard, which is caused due to an ill-fitting bearing. If the blower motor is malfunctioning, it will need to be replaced.

• There is foul odour coming out of my car AC- Foul odour from your AC can be caused due to the following reasons –

1. If your cabin filter is dirty and choked it will cause foul odour. In this case, it’s recommended to replace the cabin filter.
2. If the AC vents and ducting is dirty, clean it with the help of an AC sanitizer / deodorizer.

• The car AC cools only intermittently — This can be caused due to the following reasons

1. Accumulation of ice in the system. In order to tackle this problem, the entire system will need to be evacuated with the help of a vacuum pump and the AC gas will need to be recharged
2. A faulty low pressure cutout switch which will need to be replaced
3. Faulty compressor clutch or relay- the compressor clutch will need to be replaced.
4. Faulty AC control switch — if the ac works by bypassing this switch, then the ac control switch is faulty and needs to be replaced.

It’s important to understand that in the case of most automobile subsystems such as the AC system, one problem always leads to another. The proper functioning of this system is extremely important considering it determines the quality of the air we breathe in while driving through the polluted city streets, as well as it’s a huge factor of driving comfort. Therefore, as soon as any of these symptoms have been identified, it’s always recommended to address the issue at once. Thankfully Cartisan can do just that, with convenience, by bringing the service to your doorstep.

Originally published at www.cartisan.in on April 11, 2017.