Automotive Air Conditioning Information Forum

2005 Jetta wagon. Manual AC controls. Northern California and fall days can sometimes have heating and cooling on the same day. Confusing intermittent refrigerant leak. Car is pretty crappy and I can’t justify high cost repairs. Trying to figure out what is going on.

Fall 2020. One day AC is working fine and blowing cold. Next day, it is blowing warm only, compressor clutch not engaging, fans off. I assume there has been a catastrophic refrigerant leak. I can’t afford repairs so I ignore it because cooling season is pretty much over.

Spring 2021. I borrow a set of gauges and vacuum pump because I want to locate source of refrigerant leak before taking it to a shop for an estimate. System is completely discharged – zero pressure on gauges. I pump it down and to my surprise it holds vacuum. I don’t believe it and end up leaving it under vacuum for 36 hours and it holds perfectly. I’m confused. Recharge system and add tracer dye because I still assume there is a leak, maybe only under pressure. I’m shocked when the AC runs cold for the entire summer 2021.

Fall 2021. Earlier this week it is a chilly morning and there is interior condensation on windshield. I turn on defrost and heat. Immediately I get a huge smell of refrigerant and instantly turn off the blower. Later with windows open and me out of the car, I turn on the AC. Compressor clutch engages, fans are on, but warm air only. Clearly the refrigerant release was significant. I realize this must be the same exact thing that happened in Fall 2020 but I didn’t notice when the refrigerant leaked. I figure I’ll find such a big mess under the hood from the tracer dye that I won’t really be able to tell where leak came from. But when I put it under black light, I don’t find any signs of a leak at all.

I’m really confused. Internal leak? Evaporator? But why only during defrost or heat modes? Better question is how when there is no crossover between heating and cooling systems? I do not know if this vehicle automatically turns on the AC in defrost mode. If it does do that automatically, it does not turn on the AC light. I appreciate any insight or suggestions for me to investigate further.

You can easily have a leak under vacuum and not under pressure and vice versa.

The only way you are gonna get this straightened out is to buy or borrow an electronic sniffer, which is far superior to the dye.
If the dye were so good they never would have invented the sniffer.
Vacuum, then partially fill with refrigerant (maybe 20-30 psi), then sniff everywhere

Evaporators are known to be problematic. For this, you get under the car and sniff the drain tube. Refrigerant is heavier than air
Also, to check the compressor seal, remove belts, put shower cap over pulley, let it sit all night, then stick the sniffer probe in there and see if you get a hit

Your description reads like an evaporator leak to me, huge smell inside the car, PAG oil is really stinky. Get under the car, the drain tube can be hard to find, but when you do there will probably be dye on it. I'm not so sure sniffers are superior and the only way, I have a good one, but different leaks are found by different methods, snoop, sniffers, dyes, any one of them might be successful.

Your car runs the compressor in defrost or mix mode, yes it's automatic, if the ambient is high enough, the compressor will run. they usually don't light up an A/C indicator because they don't want to confuse drivers.

MY ERROR- CORRECTED
Above I said to remove the hoses from the compressor to check for a shaft seal leak.
I meant to say remove the belts.
I have corrected that in the post
Sorry

Thanks for the helpful information! I'll hunt around the evaporator drain tube and see what I can find.

Is it correct that if there is an evaporator leak, it should leak no matter what mode it is running in? After the leak in fall 2020, I ran the AC easily 100 hours over summer 2021. And then bam, leaks when I changed modes. Does the mode change being related make any sense at all? I can't figure that out.

Not really