Troubleshooting AC Issue - What dye to use to check for leak

[C5Longhorn]

I'm going to buy a can of freon with dye to try and pinpoint an AC leak I have. I notice they sell both ultraviolet and red. Is the UV better since it won't blatantly show up as a stain like the red dye will?

Also, how much is needed? Assuming I don't have much left in the system, do I need a 12 oz. can or will 3 oz be sufficient for testing?

Thanks,

Rick

[Bugman Jeff]

I prefer the UV die. I'm a bit colorblind so I wouldn't be able to see red stuff in small quantities. The UV die, with a blacklight flashlight and yellow tinted CSI safety glasses shows up great in a dark garage(the yellow tinted glasses make a HUGE difference in seeing the glowing die).

You really just need enough so that the system will operate normally. Depending on how big the leak is though, it may take awhile for enough dye to accumulate to be visible, so a full charge might be the way to go. IIRC, the amount needed for a full charge is on the AC system sticker under the hood.

Also, make sure the can is just freon and dye, no sealers or "system conditioners." Sealers and the like often cause more harm than good.

[C5Longhorn]

Thanks, I'm planning on using this stuff. Any problems with it?

[Bugman Jeff]

Should be fine. Inspect the car well before recharging it too. Other fluids, particularly antifreeze, can also glow in UV light. You want to be sure to take note of any pre-existing glowing spots so that when die starts showing up, you now it's recently appeared. It's also possible that someone at some point has already put dye in the system and your leak is already visible.

[C5Longhorn]

Great tips, appreciate the input