AdvicesAircon Not Working? Common Issues And What You Can Do To Fix It

August 19, 2021cargarage0

A broken car air conditioning unit isn’t just frustrating, it’s potentially dangerous. 

Without the right conditions, driving on a hot day can be tiring, irritating and draining, leading to a loss of focus on the road. Aircons help to alleviate this issue by providing car owners and their passengers with a consistent flow of refreshingly cool air, especially in packed cars lacking a steady supply of fresh air. 

While a simple mechanism in principle, a number of common issues can lead to your aircon not working next time you go to drive to work or school. Today, we’ll take a look at some of the most common car aircon issues, what you can do to fix them at home and when it might be time to call in an expert. 

Troubleshooting your car’s air conditioning

Noticed a problem with your aircon but you’re not quite sure of the cause? Here are some questions you might be asking yourself about your car’s internal systems: 

Why does my air conditioning have a weak air-flow?

There are a number of faults that may cause weak airflow in your air conditioning system. 

These issues range from minor faults such as blocked air ducts to more substantial breakages within the internal systems, such as evaporator damage. 

A weak airflow may also be a sign of mould or mildew growth within the evaporator clogging the vents and breaking the seal within the system. This is particularly common during cold, winter months where the aircon remains off. 

How can I test if my air conditioning system has a leak?

Testing your air conditioning for faults is tricky without knowledge of the particular system, so it’s worth consulting a professional for advice and guidance. 

They will have the equipment to check for common signs of leaks, such as refrigerant dyes that only appear under black light. 

What causes a leak in the air conditioning system?

Moisture and age are the main causes of a leak within your air conditioning system. 

When moisture mixes with the aircon refrigerant it produces a corrosive acid that can erode and damage the entire aircon.

This moisture may find a way to enter the system through old rubber seals and hoses that have lost their elasticity over time.

This can be a more costly and time-consuming fix so it’s best to hire a professional to look at. 

Most Common Problems With Car Air Conditioning

Air conditioning can be quite temperamental in old vehicles, particularly when you first start them, or at the first sign of hot weather after a cold winter. Here are some common problems you might encounter in both old and new vehicles: 

Air conditioning is not as cold as it used to be

There are a number of reasons why your air conditioning may not be projecting cold air in the same way it used to. 

Older vehicles can suffer from a range of loose or broken parts, such as the hose or a seal. This can happen throughout the system, depending on the make and model of the car. More serious issues may be the cause, such as the condenser or evaporator suffering from faults causing them to malfunction, or the motor within the compressor burning out. 

An aircon getting colder is not just a sign of age. Vehicle parts can naturally wear away, but you shouldn’t accept that as a given. 

Air conditioning starts cool but goes warm/blowing hot air 

An air conditioning that starts cool before quickly transitioning to blowing hot air in your face might be the sign of a problem with the clutch within the compressor. This fault can lead to the compressor failing to maintain the correct pressure, leading hot air to flow throughout the system. 

A clogged expansion valve has also been known to cause this issue, resulting in a reduced flow of refrigerant into the system’s evaporator. 

A more serious and long-term issue may be a leak within your air conditioning system. This leak may be the result of moisture entering the system, mixing with the refrigerant to produce corrosive acid, damaging components throughout the vehicle. 

In short, the most common causes of this irritating and distracting issue are:

  • Damaged cooling fans
  • A blocked or broken condenser
  • An internal obstruction
  • An electrical fault 
  • Low refrigerant levels

Air conditioning smells bad

Greeted with a less-than-fresh smell when you start your car and switch on your aircon? 

No, your car doesn’t need a clean, but your aircon might (or something more substantial). 

Here are some of the most common reasons for this problem: 

Damp Smell

A distinctive damp smell of mildew inhabiting the air coming through your vents is generally a sign of bacteria and mould build-up. This is particularly common in older cars that have been neglected for a number of years. Without regular cleaning behind the dashboard, bacteria can develop and grow, infesting the internal workings of your aircon. 

Cleaning this section of your car and ensuring you’re running your aircon for a short period every couple of weeks can avoid the buildup of bacteria, as it dislikes the drying effect on the excess water found on the coils. 

Pungent Odours 

Air filters clogged with dirt, dust and stagnant water can emit a foul odour. Much like the damp smell of bacteria, this is usually the result of years of buildup and neglect. 

Chemical / Sweet Smell 

A sweet, chemically smell when you turn on your aircon might be the sign of a leak within the system.

The radiator or housing unit for the coolant may also be experiencing a leak, emitting this offputting smell. 

A Smell of Gas 

More worryingly, the smell of gas can be a sign of more complex issues with your air conditioning. 

An aircon gas leak should not be taken lightly

A gas leak can be determined in your air conditioning when a smell of gas is emitted after you turn on the system. This waft will often appear when the system is first turned on and fresh air is sucked into the vents, pushing out gas that has built up within the unit. If you smell gas in your vehicle, consult an expert. 

Air conditioning won’t turn on

An aircon that won’t turn on can lead to a deeply unpleasant driving experience, particularly during the hot summer months. 

This problem may be the result of several faults, including:

  • Overheating air conditioning systems
  • Burnt out fan
  • Broken dial, stuck value, faulty wiring or a blown fuse
  • Obstruction in the air duct
  • Disconnected battery (this will cause larger issues throughout the vehicle) 
  • Low coolant levels

So, what should you do if you’re struggling to get your aircon to turn on? As this fault can be caused by many, often delicate, technical issues, it’s worth contacting your local garage or specialist to take a look at the fault. 

However, low coolant levels can be diagnosed by listening for the sound of the compressor kicking on and off. If you can’t hear it engaging, it’s likely a sign this is the fault leading to a broken aircon. 

Make sure you run your aircon for a couple of minutes every couple of weeks throughout the winter months to keep the system in working condition and avoid the build-up of disruptive substances. 

Air conditioning won’t turn off

You might be experiencing issues with a car air conditioning system that simply won’t turn off. This can make driving very uncomfortable during winter months and, in extreme cases, drain the battery if this problem persists even when the engine has been switched off. 

This problem may be the result of several faults, including:

  • Broken selector switch 
  • Shorted blower motor relay
  • Shorted blower control circuit
  • Faulty or loose ribbon cable
  • Broken controls stuck in the ‘on’ position 

An air conditioning system that won’t turn off is a problem worth solving for a number of reasons, including reducing the amount of fuel used to power the systems and avoiding sickness and concentration issues while driving. 

As this issue can be the result of a number of different factors, it’s worth checking in with your local garage or expert for a consultation on your vehicle. 

All of these issues can be signs of a deeper issue with your aircon and even your car at large. If you’re experiencing any of them avoid tinkering yourself and consult experts to ensure your stay cool on your next drive. 


Is fixing your air conditioning expensive?

A full revamp of your car’s aircon can get quite costly, so consider shopping around and trying to access the problem to some extent yourself, to avoid additional assessment costs. It might just be that your air conditioning requires a clean. 

Can I tackle these solutions by myself?

Your owner’s manual may provide some insight into technical issues with your aircon. 

Can similar problems occur with the car’s heating and thermostat?

Yes, other parts of the car’s temperature control can be affected by the development of mould, inconsistent usage and many of the other factors listed in this article. However, they should be accessed on their own present faults. 


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