AC leak detection: Options

[RickM]

I posted this on an existing thread....it probably deserves it's own.

Questions:
What are the options for finding leaks in the AC system?

I've seen dye that is poured into the system then checked with a light.
What other techniques are available? Is there a can of refrigerant that has the dye incorporated into it or do I have to "open" the system to introduce the stuff?

Oh yeah, I've heard about the sniffers but for occasional use might be overkill......

[AFJuvat]

Shoot in a UV dye and look around fittings with a black light You introduce oil and dye in the low pressure side of the compressor (usually the lower hose with the schrader valve facing the rear of the engine)

Start at the fittings on the compressor, the compressor body behind the clutch and pulley; then where the lines connect to the condenser, then check the evaprator in the smugglers box.

Also, run the air, and tape a piece of white paper over the vents - any dye released through the evaporator to the vents will stick to the paper.

The dye will show up as green splotches - very obvious.

Snoffers are good up to a point - rather expensive and can give false positive readings (particularly around some shop chemicals)

AFJuvat

[RickM]

AFJUvat,

Thanks for the info. Is the dye/oil in a presurized can, like the refrigerant, or do I need a special tool to introduce it into the system.

[AFJuvat]

For R-12 systems it is getting harder and harder to find. You may want to bite the bullet and have an AC service shop shoot the dye in your system for you. (usually $20) then all you need is a black light to detect the dye.

AFJuvat

[techguy]

4 Common Tests for leaks

(1) Black light to detect dye if installed previously
(2) High pressure nitrogen usually to about 240psi then check fittings for leaks
(3) Electronic Sniffer test, not sure if it detects the freon or the nitrogen
(4) Vacuum Test


I know since the A/C in my other car (mini van) went warm and after 2.5 hours and all 4 tests they still could not find the leak.

Pete

[Don Wohlfarth]

Start with a visual check on the underside of the engine lid. You are looking for a oily mark that could indicate that the compressor seal is leaking. Continue your visual check of all the hose ends, you are looking for oily residue. If you find a really grungy hose end that would be a good place to continue the search with soap and water or electronic leak detector.
Another leak detection system utilizes a black light where you inject a fluorescent dye into the system and shine the black light all over to find the leak.
Nitrogen is sometimes used when there is a small leak. You add nitrogen to the system and build the pressure up to 250# with the a/c off and then look for the leak with a electronic leak detector. The nitrogen mixes with the refrigerant and the detector sniffs for trace amounts of refrigerant.
If you have a leak in the evaporator or condenser coils you generally have to use either the fluorescent dye or nitrogen.
Several years ago there was a refrigerant that had a red dye already mixed into it, what a *&%$ mess. The fluorescent dye is not as bad.
Forgot about the vacuum test. A leak free system will hold a vacuum. If you cannot hold a vacuum you have a leak. It will not tell you where the leak is located.