finding a leak in a mini-split

Isolate the components.

Pressure test the air handler and line set separately, 600#'s N2.

I like the H10 Leak Detector.

NEVER use dye in a mini split.

The dye isn't actually a liquid, it's finely powered fluorescent minerals. What happens is it settles out. I had a Mitsubishi that someone put dye in. I took the compressor out, dumped the oil, rinsed the compressor with denatured alcohol several times, & was still getting small flakes out. It was a total loss, we ended up replacing the outdoor and indoor units.

Have any of you ever experienced this? I had a leak in my self-installed mini split. I bought a sniffer and it detected a leak at one of the 2nd floor heads. I got a replacement under warranty after sending a video of the leak detector going off near the fins of the head unit.

I replaced it but the leak persisted.

I dug deeper and found it for real at a place where I had spliced the line set (I would not do that today).

I think the refrigerant migrated up the lineset insulation all the way to the head where the sniffer detected it. I have always felt guilty about that warranty replacement that probably was my fault.

Also, I swear I could smell it in the room when lying quietly, but it was VERY subtle

yep is was buried in a line set run guard thing on the exterior wall but at least it was near the ground. Definitely a case of looking for my keys where the light is stronger

IDK if you were referring to my post re dye, but Mitsubishi will not warrant a unit that has dye in it. Perhaps other mfgrs allow it, I may have been too general.

I've seen dye work fine (well, messy as h#!!) in regular splits and automotive applications. IDK what it is about Mitsubishis, perhaps the metric oil (AB or something , I forget) is the cause, but it was something to see. It'll piss me off something fierce to get it in my manifold, though.

mine will go out of balance if i tap the sensor on anything. had it go off lots that way, never actually found the leak that way.

those #’s are conservative!

the wheatstone bridge in the refrigerant detector.

like it is alarming because i smacked it on the firewall next to the evaporator connection, not because it encountered refrigerant

mine is a very old d-tek that i bought off ebay a decade or so ago.

If you used a white line set, more likely than not it's the line set leaking. We had so many leaks when the white line set was used, we went back and replaced the line sets and haven't had any problem since. We never use any line set with white armaflex.

Bob Cermignano

Ardmore, Pa.

My wife sold a brand name leak detector that worked as well as any of them (not) for $5. at our yard sale snd I was upset at the price but glad that it was gone. It also would go off at randome or when it got bumped. I use an ultrasonic detector and dye . The only ultrasonic that I think works is the one that is made by superior signal called Accutrak. It has been marketed by Kent Moore and some others also. I'm glad to hear that the dye is mineral ad you cansee it separating in the tubes sometimes. It plugged up a couple of the tubes and would not come out . The ultrasonic is a bit tricky at times but still the best. Ionce was looking for a leak in an ice machine in my garage and followed the sound and it was coming from bugs in my garden. Alos flourescent lights ballasts and neon lights bother it and fool you.

I am a refrigerant system puriest. Only two fluids belong in a vapor compression system - Refrigerant and Oil. 😎