Diagnosing and Fixing an AC Freon Leak

It’s summer, you’re driving, and you flip on the air conditioning. But only warm air, or cool, not cold, air blows out of the vents. What’s wrong? You could have an AC Freon leak, meaning that refrigerant is leaking out of a crack or hole in your air conditioning system. Follow the steps below to diagnose and fix an AC Freon leak. If you have any questions, always consult a licensed auto mechanic.



Don’t Just Top Off with Freon

A working AC system is a sealed system, so it shouldn’t spontaneously leak refrigerant. If you’re low on Freon, it’s because you have a problem, most likely a leak. Though the Freon used today, 134a, is better for the environment than the refrigerant used in older cars, called R12, it still isn’t something you want leaking out into the air. So don’t just top off with Freon and keep driving; diagnose the problem and fix it.


Visually Inspect the AC System

Large leaks are visible to the naked eye. Before you do anything else, scan the AC system, especially fitting attachment points and pressurized lines, for signs of oil buildup. If you see an oily substance at a particular point along your AC system, there’s a good chance you have a leak there.


Add Freon to Raise the System Pressure

Standard leak detectors work best when the AC system is running close to normal pressure. This means that if you’ve lost a lot of Freon, you’ll need to add more. Add just enough refrigerant to bring the AC gauge reading over 50 psi.


Use an Electronic Leak Detector

You can purchase a hand-held electronic leak sniffer to check for Freon leaks.
* a) Make sure the tip of the electronic leak detector is clean. A sensor covered with dirt or oil won’t accurately detect leaks.
* b) Run the sensor along the AC system at a rate of one inch per second. Hold the sensor relatively close to any pipes and fittings, as Freon is heavier than air.
* c) Note the location of any leaks detected by the electronic leak detector. Depending on the model, it will beep, buzz, or flash when escaping Freon is detected.


Use a Black Light or UV Detector to Check for Leaks

If your refrigerant contains UV dye, or if you want to add UV dye to the AC system, you can check for leaks using a black light or UV leak detector.
* a) If the Freon in your AC system doesn’t contain UV dye, add dye using a dye injector. Let the AC system run for several minutes to distribute the dye.
* b) If you purchased a UV detector kit, put on the yellow glasses that came with the kit. Run the black light or UV detector along your AV system components. Any leaking refrigerant will light up under the black light. Note the location of any leaks.


Repair Small AC Freon Leaks with Chemical Sealants

Some AC Freon leaks can be easily repaired using a chemical sealant. For small leaks at any point along the system, try injecting a commercial leak sealant into the system. Run the AC for several minutes to distribute the sealant, then check again for leaks.


Replace Any Damaged Parts

If you have the know-how, you can replace any damaged or leaking O-rings or AC system components yourself. After installing the new parts, hook an AC vacuum pump up to your system and let it run for about 15 minutes. Remove the pump and watch the AC pressure gauge. If the vacuum holds, you’ve fixed the leak. If it doesn’t, a large leak is still present in the system.


Visit an Auto Mechanic

If all else fails, visit a licensed auto mechanic. Shop repairs to minor AC leaks are relatively inexpensive. If you don’t know what you’re doing, messing around with your AC system can cause larger problems. It may make sense to visit your local auto shop and let them fix your AC Freon leak.

Few car problems are more annoying than a broken air conditioning system. Often the culprit is an AC Freon leak, in which refrigerant escapes through cracks in the system. The first step to fixing an AC Freon leak is locating the leak. You can do this by visually inspecting the system, or by using an electronic or UV detection kit. After you’ve located the leak, you can attempt to repair it yourself, or bring your car to a licensed mechanic for professional help.