Testing Your AC System for Leaks with a Dye Test

ac vents
Keep your auto air conditioning charged and leak free. Getty

If you've been driving around with hot air coming from your air conditioning vents, it's definitely time to recharge your AC system. These days, recharging it yourself isn't too tough a project, and the kits you can buy at your local auto parts store aren't hard to use. It's a perfect do it yourself project for the weekend wrench turner. But what if you have recharged your AC system, and you got nothing out of the deal?

Or are you in a situation where you have to recharge your air conditioning every season due to a slow leak you can't seem to trace? If this is the case, you may need to perform a type of leak detection procedure known as a dye test. While there are expensive air conditioning leak detectors available from major tool sellers, in most cases the disposable, over the counter dye-based detection kits work very well. Your car or truck's air conditioning system operates on a tightly closed circuit of circulating freon. There shouldn't be even the tiniest leak in the system. With the amount of pressure the AC compressor produces, it doesn't take much for a tiny leak in the plumbing or hardware to render your system useless and leave you sweating to the oldies on the way to work. Dropping it off for air conditioning service at the local garage can turn into a very spend proposition in a hurry. They do have superior equipment for leak detection, refrigerant collection, and overall diagnosis, but the price tag will reflect the investment the shop had to make in this expensive equipment.

 

Definition: A dye based air conditioning leak-down test uses a colored dye to find freon leaks in your air conditioning system. Using this test, a colored dye is injected into the a/c system which will be visible under UV (ultra-violet) light at the point of a leak anywhere in the system. The test is performed under full pressure with the air conditioning system closed (sealed as if you were driving under normal conditions).

If you're using the auto parts store version of this kit, you'll simply inject a small can of UV dye into the air conditioning system through the same charging port you use to add freon. With the dye injected and enough pressure in the system, simply run the AC and use the special UV light to look for any area that is fluorescing. Even a tiny pinhole leak is easy to spot when you're using this blacklight method. I love it. You'll also be able to tell which leaks are tiny and which leaks are major, leaving you free to make smart decision in terms of your budget. You may decide to fix the massive link in your condensor right away but leave those two pinhole leaks in the high-side line for another day. Performing a leak test is a good idea if you are thinking of recharging your AC system because recharging a leaking system is a waste of time and money.

If you're curious about how your AC works, check out How Your AC System Works and you'll be one step closer to air conditioning expert.

Also Known As: Freon Leak Test, UV Test

Common Misspellings: AC, froen