Air Conditioning Troubleshooting Tips and Advice From a Mechanic

Before you start air conditioning troubleshooting you need to realize that it is not as easy as you might think. There are many things that can go wrong when trying to fix your AC system yourself.

Probably the most common problem that people run into when attempting DIY A/C repairs is that they get dirt and other debris in the system and/or they don't put the correct amount of freon in the ac system.

When the system is not flushed of all debris and old oil, it will never cool right. If there is too much or not enough refrigerant then it will also never cool how it should and it could even pose a danger. Modern air conditioning systems MUST be clean and have the correct amount of freon in them in order for them to cool properly. Here's more information that will help you sort it out air con troubleshooting...

How Your AC System Works

It is a very little known fact that a fully functional air conditioning unit does NOT run out of Freon. Freon (R-134a or R-12 in older systems) is pumped through the AC system by the compressor.

The compressor compresses the gas and pushes it into the condenser. The condenser causes the gas to turn into a liquid. This high pressure liquid has now lost a lot of heat and is ready to take in heat from the interior of the car. It is pushed through a drier which keeps the liquid dry, then it goes to an expansion valve (there are other names for this device but they work in a similar manner).

The expansion valve pushes the liquid through a very small opening thus creating small droplets of refrigerant that is then pushed through the evaporator. In the evaporator the liquid refrigerant (R-134a) changes from a liquid to a gas. In this process it takes in large amounts of heat and thus the air is cooled.

The low pressure gas is sucked into the compressor. This process is repeated, using the same gas over and over. Nothing comes in and nothing comes out. The water that you see leaking from the car on a hot day when you have been pumping the AC is due to condensation on the cold bits and does not come from within the unit. Just like water droplets gathering on the outside of a cold glass of juice.

To put it another way, the gas is not used up, so it continues to do what it does, as long as it stays inside your car’s air conditioning system. The fridge in your kitchen works on the same principle as your auto AC and how many times have you heard of someone refilling their fridge with Freon?

Air Conditioning Problems in Cars

Air Conditioner Leaks

Leaks are, as I mentioned, not the only possible culprit. Simplistically put, you may require air conditioning repair when the mechanical or electrical bits break. The bits include things called evaporator coils, compressors, electric motors, condensers, belts and pulleys. Like all electrical and mechanical things, they can wear down and break.

Air Conditioning Evaporator

Evaporator coils are generally not worth repairing. The cost of reconditioning one of these tends to exceed the cost of replacing one with a new part. A new part will last longer in any case.

A/C Compressor

Compressors can be repaired, depending what the problem is. If you just have a problem with a compressor clutch then it can sometimes be replaced. This is becoming less common as companies are opting to manufacture compressors that do not have serviceable clutches.

Most of the time you will just have to replace the compressor. These are not cheap. Including labor, you are probably in for anywhere from $100 to $1000.

A/C Belts and Pulleys

You may know what a belt or a pulley is. Your engine probably uses several of them. As the engine works, it drives not only the wheels, but other components such as your alternator and power steering.

Ever noticed how the wheels are impossible to turn when the car is off? Your engine is connected to these other things by a pulley system. A pulley is a wheel which has either has teeth or grooves on it. The engine turns a pulley. A belt, which is a very strong rubbery thing, fits into the grooves of the engine pulley and in turn drives the air con’s pulley.

Fairly simple. Belts and pulley’s wear out and need to be replaced. Replacing them seems easier than it is unless you have the right tools. In order for them to work properly, they need to be under the correct tension. Something called a tensioner, does just that. Your mechanic can replace the AC pulley quickly and if you have the right tools you can do it fairly quickly as well.

If you decide to replace your AC belt yourself then be sure you have a serpentine belt diagram. There is usually one located on the hood or somewhere in the engine compartment, but if you can't find it then you need to get a repair manual that has one. No matter how much you think you remember how it goes, you will forget!

I am all for the enthusiast tinkering about or those with tight purse strings doing some DIY to save a few dollars. Most of the time auto air conditioning troubleshooting is not worth the effort or the money to risk doing yourself. One exception to this is if you are diagnosing an electrical problem in your AC system. As long as you are not messing with the Freon you can probably do some of the diagnostics yourself.

DIY or Take It to a Mechanic?

A leak is not the only possible problem with auto air conditioning. Before I move on to other possibilities let me be clear: go to your mechanic. You are not going to fix the leak yourself. Air conditioning troubleshooting is not an easy DIY job.

I would not start squirting dye I bought at the corner store into the air conditioning system to find a leak. The dye used by the professionals is proven not to damage anything. That being said you can find tracer dye at any good auto parts store. However, you have to get this dye into a pressurized ac system. You can get a kit at auto parts stores and even Wal-mart has the fitting to put it into the air conditioner.

The problem though, is that you don't know what you are putting in with these kits. If you put it in then have to take your car to a repair shop they would not touch it because they would have to use a machine that would suck it into their refrigerant bottle and if they don't know what it is they certainly won't put it into their stock (as this would contaminate their whole bottle).

You almost certainly don’t have the equipment do this safely and it is not worth buying the equipment unless you are planning to open an air conditioning troubleshooting shop. A repair shop will have an AC machine that is used to vacuum out all of the old refrigerant, ac oil, ac dye, etc. It will then be used to put the correct amount of refrigerant, oil and dye back into the system.

Kits are available but chances are pretty good that even if you were to find the leak, fixing it is hardly ever straight forward. Every time you get it wrong, you are going to pay to refill the gas and then try again. I doubt very much that you will source the parts for less than an auto repair shop, who buy parts in bulk.

You get my point - Air conditioning troubleshooting and repair is best left to a mechanic.

If you still have any unresolved vehicle problems or questions, you can ask an auto mechanic online. For expert answers specific to your vehicle's make and model, I recommend JustAnswer Car. They have a large pool of certified mechanics to answer your questions for a small fee and you can also browse their answers to other users for free.

Air Conditioning Ripoffs

What then, begs the question, do those fellows do, who promise air con refilling at a fraction of the cost?

In my opinion, they take your money and claim to be doing air conditioning troubleshooting and repair. In exchange, they do put more gas in your car and then they hope that the leak in your AC is small enough that you won’t bother them again for a good while. When it eventually runs out, you go back like a good customer and give them more money.

However if the leak is significant, they will send you away. They will say that you need to go to your mechanic or AC specialist because the issue is not the gas. It never was. The loss of gas was just the symptom. The kicker is that once the problem is repaired, you will have to pay to have the system regassed again. They probably don't even know how to do air conditioning troubleshooting.

Only on rare occasions, is the cause for loss of the Freon a temporary one, in which case, I would be wrong about a quick refill sorting the problem but I am willing to bet that my gloomy prediction is almost always right.

How to Make Your AC System Last

To make your auto AC last longer, you should minimize the wear and tear. In other words avoid using it, unless you have to. If you do use it, close the windows and turn the air recycling on. This way, the AC does not have to work as hard to keep cooling the incoming hot air and more importantly does not stop and start continuously.

If you live in a cold climate try to remember to run the AC every month or so. There is oil in your air conditioning lines and when the AC is off it does not circulate. It is good to circulate it every once in a while to keep the seals inside these lines lubricated. This will help your AC system to not leak. Air conditioning troubleshooting is a challenge for most car owners and better left to professionals.