Air conditioning not working? It might not be broken!

Hooray, we now have warmer weather….finally! Let’s hope it lasts the summer this year.

So, you finally get the rare chance in this country to use the air conditioning in your car, but instead of feeling a lovely cool breeze on your face catastrophe strikes & warm air shoots through the vents! Sound familiar?

At this time of year my garage receives around 10 calls a week from concerned customers wanting help with their aircon problems. Most, including me before I got into this industry, don’t understand how their aircon system operates and assume it is broken and going to cost a fortune to get repaired. Not true! For a good majority of our customers, the system simply requires re-gassing.

So let me try to explain in Jennifer speak how the air conditioning (aircon) system works and what could be happening to your car.

Like your body, the aircon compressor is the heart of the aircon system, and Freon gas is the blood. The compressor pumps Freon throughout the aircon system, either the older type R12 (which costs as much as gold it seems these days!), or the new environmentally-friendly R134A Freon. Any way, my point is it’s Freon!

This Freon is a gas and liquid combination that is compressed and circulated throughout the air conditioning system. The compressed Freon is pushed through the system under pressure and is passed through different sized metal and rubber hoses and a special valve called an expansion valve that cause the gas to expand and contract.

This expansion and contraction makes the Freon gas very cold. The cold gas makes its way via metal lines into the dash area of your vehicle to the evaporator core.

The evaporator core is like a small radiator, except it has cold Freon circulating inside and not hot antifreeze. A small fan (the aircon blower fan which you control from the control panel on the dash) sits in front of the evaporator core and blows air across this cold evaporator and then through the vents inside your vehicle.

The objective of the air conditioning system is to remove the heat from inside vehicle. This heat is removed by the Freon with the help of the aircon condenser located at the front of the car (usually in front of the radiator). The Freon coming back from the evaporator carries the heat from the cab to the condenser via rubber and metal hoses. Just like your radiator, the condenser is lightweight aluminium with many internal winding coils.

The Freon travels through these coils, and in between these coils are small slits or fins that the Freon is forced through. The condenser will have an electric cooling fan mounted in front or behind it to push or pull air through these fins to remove the heat from the Freon. Some vehicles still use the old fashioned fan blade driven by the engine to pull air across the radiator and the condenser.

Okay, so maybe this isn’t quite the Jennifer speak I’d intended, but believe me, this is just an overview on how the air conditioning system works, and it is very general.

A few causes of low cooling efficiency or no cooling at all at idle (stationary/low speed) are:

• Lack of air flow across the condenser. We ensure the electric cooling fan motor near the condenser is coming on, or in models that are equipped with a fan blade we make sure this fan is turning and is turning very fast.

• Low Freon levels. Freon level and pressure are checked - by law, this must be carried out by a qualified air conditioning mechanic, like ours ;-). This is one of the most common reasons why your aircon isn’t working. The system needs re-gassing every one or two years.

• Overheating. If the engine is running hot or overheating, it can have a noticeable negative affect on the aircon system. Some cars have two electric cooling fans, one for the aircon condenser and the other for the radiator. Usually at idle on a hot day with the aircon on both fans will be on. We check to ensure they are both working properly. 

When your car is travelling at higher motorway speeds, the compressor is pumping the Freon throughout the system much faster and harder than at idle. There is therefore a dramatic increase in air flow across the condenser due to higher mph winds, and the engine is usually operating at a cooler, more efficient temperature as well, thus allowing the air conditioning system to operate efficiently.

So an air conditioning system that is somewhat low on Freon can still feel comfortable at motorway speeds due to the added air flow across the condenser which can overcome the ill effects of slightly low Freon. Periodic air conditioning performance checks and a service are the best way to keep the system in great shape.

The last point I wanted to make (and I loved this tip when I found out about it myself!) is this. Use your aircon system in the winter months too! It clears the ice from your windscreen a lot faster!

A typical aircon service will cost around £25-30 + VAT. It includes a anti-bacterial treatment and pollen filter.

A typical aircon re-gas costs £50 + VAT. You can also ask for a regas with a special UV dye if you suspect you have a leak which makes the leak much easier to detect. This usually costs around £10 more but saves a lot of labour tome (and cost!) in the long term. A decent respectable garage such as ourselves ;-) will offer a free re-gas should any faults then be identified with the system.

Of course a cheaper option is to

wind your window down!

By law, only certified garages with trained, qualified mechanics can offer an aircon re-gas service though, and there aren’t many of us around in the Exeter area. So don’t get taken in by those cowboys (or girls!) out there offering cheaper “cash jobs”, which then aren’t under warranty and they won’t be able to repair any identified problems if the aircon re-gas doesn’t solve the problem.

Anyway, whether your air conditioning system is working or not….enjoy the summer and this lovely fine weather we’re having!