Air Conditioning Leaks

freon leak detector kit with dye

In my opinion auto air conditioning leaks are the most common cause of automotive AC systems not blowing cold air out the dash vents.

What can happen is the vehicles Freon will leak out and reduce the total pressure in the system. Then the low-pressure cut out switch will disengage the compressor when the low side is detected below 25 psi.

This safety feature is to protect the compressor itself. I have seen professional and driveway mechanics bypass the low cut out switch for testing. This should never be done and is not recommended.

The car AC compressor can be damaged quickly when the freon is low because it contains the lubricant needed by compressors. When internal damage occurs it can spread metal flakes through the entire air conditioning system.

For these reasons replacement of this primary component is a very expensive auto repair. Note that when the system pressure is low and the compressor clutch disengages it is just like having the AC switch turned off completely.

Therefore testing for air conditioning leaks properly is one of the most important tasks when it comes to troubleshooting a system. Keep in mind that over a long period of time, all air conditioners will lose or leak out some refrigerant. I went to a Delco AC training class and the instructor said that on average, an AC system could lose up to 2 ounces of Freon A year and this would be considered normal.

Finding Automotive Freon Leaks

ac compressor sealed

As I mentioned before in previous articles about how the air-conditioning system works, the Freon contains the lubricating oil charge necessary to protect the compressors internal moving parts. We can also use this refrigerant oil to find leaks.

The visual presence of oil around a fitting or pressurized line is a strong indication of a freon leak. So my first step in freon leak diagnosis is to perform a very careful visual inspection of the entire system.

Although this is always my first step for diagnosing Freon leaks it is not always effective in finding the exact problem. In fact, this visual inspection will only uncover large to extremely large leaks. A more common air-conditioning problem would be small leaks that allow Freon to escape over long periods of time. So to follow will be some methods to detect these small leaks.

Electronic Automobile AC Leak Detectors Reviewed

My Robinair leak detector is the second tool I will use in my fight against air conditioning leaks. This is the preferred method of leak detection because it is safe and effective and can be used with all types of refrigerants. This leak detector is a hand held battery operated electronic leak sniffer.

The test probe on the end of the leak detector is moved about 1 inch per second in the areas of suspected leaks. Make sure the tip is clean before testing begins. I usually go for the high pressure side fittings and O-rings first. Also note that the refrigerant is heavier than air. So I will run the leak detector just below these fittings and lines.

The Robin air leak detector has an alarm that will go off when it detects the presence of a Freon leak. Note on some other models they may have flashing lights or a buzzer. Also some leak detectors are specialized to detect only certain freons (example: 134a) but they all are designed to alert you when they sniff the refrigerant.

Are Fluorescent Dye Leak Detectors Better

Most auto repair shops that I have worked at including the one I work at now has a fluorescent dye tracer system for finding stubborn leaks. To find refrigerant leaks using the fluorescent tracer system, you first have to install the fluorescent dye into the AC system.

Always follow the instructions and do not install too much dye! Too much can reduce the cooling efficiency of the system. Different refrigerant dye leak detectors will accomplish this in different ways. The type we use at work has a device that looks like a caulking gun and a hose that connects to the low side fitting.

Then you actually push the dye into the low side with the engine running and the compressor engaged. Next you run the air-conditioning system for several minutes to distribute the dye evenly. Then you put on your yellow glasses and examine the system with a fluorescent light.

The fluorescent dye shows up easily wearing the yellow glasses. Sometimes the results will yield something you do not want to find. For example, the last time I used the fluorescent dye system I did not see any leaks in the engine compartment.

But when I examined the evaporator case inside the vehicle, the fluorescent dye was laying in a large puddle on the bottom of it. This meant the evaporator itself needed replacement. This is not a fun job on most vehicles. In some cases the dash has to come out completely.

What about Air Conditioner Leak Sealer for Cars

A very popular selling item is refrigerant with leak sealer added. This item will only seal very small leaks. I have used the stuff pictured to the right "super seal pro" and it does work in some situations.

The Freon leak sealer works best when you have low side system leaks. And if you happen to have a small leak from an O-ring on the low side this stuff works well. If you have a leak on the high-pressure side chances are this sealer will not work for you.

Although if the leak is small enough and from an O-ring on the high side there is a 50-50 chance the stop leak will help. And when I say help, I mean that it will even slow the leak down further but it will most likely still leak. The most common scenario from using an air conditioner leak sealer is systems will still leak but may only need to be charged once a year.

Usually a charge installed in the spring will last till the end of the summer in the best-case scenarios. But with the cost of AC repairs quickly becoming one of the most expensive auto repairs of all, $35 a year to stay cool does seem like a fair price.

Just remember I mentioned it may not work at all and you will wind up having to diagnose your air conditioning leaks the old fashioned way. It is quite possible that physical repairs or the replacement of leaking AC components will be required.

If you decide to go ahead and replace leaking ac parts it is important to pull a vacuum on the system to remove any moisture after the repairs are complete. Moisture can cause many problems but can also freeze up and create hard to diagnose blockages in the system.

Give this automobile AC repair page a bookmark or share. Then come back to explore the car AC information that follows.





I'm a strong believer that it is easier to fix something when you understand how it works fully. And this is what the car AC section of this website is all about. This next link will take you from air conditioning leaks to automotive air-conditioning.

My best page about this subject provides a diagram that is easy to read and provides an explanation of how automobile air conditioning works.

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If you need specific car repair instructions for replacing ac components on particular cars then take a look at my online car repair manuals section that includes a video demo.

On the you fix cars home page you'll find a brief rundown of what else is available on this auto repair website. You'll also find more information about the mechanic that built it and why he thinks a lot of people can do their own Diy car repairs.