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-   -   Chevrolet Forester: Strange A/C problem (https://www.team-bhp.com/forum/technical-stuff/137326-chevrolet-forester-strange-c-problem.html)

The AC on my car (Forester) has been having issues for some time now.
Within a span of 6-7 months, I have taken the car to the workshop 3 times as the AC gas seem to be leaking. Each time, they have refilled the gas saying they are not able to diagnose any leak. After every refill, it seem to work well for some time (2-3 months) and the leaking happens all of a sudden rather then a gradual drop in the cooling functioning.
According to the workshop folk, this is unusual and they are not able to detect any point of 'leak'.
I am just back with fresh refill and have been advised to watch out for any hissing noise (indicating a leak).
Any pointers from the experts on what could be the issue here?

Well, proper AC workshops fill in gas with a colouring agent that lets them check for leaks. What has your workshop tried in their quest to find a leak? It isn't great advise to ask the customer to listen to a nearly inaudible (small leak) hissing sound.

Apparently they did apply the colouring agent when they did the previous fill but that was only to the parts under the bonnet. This time they have checked the evaporator as well.

I am no expert in car ac's and hence don't know about colored gas. But to test copper piping for leakages in ac installation on our sites (residential and commercial), we do a nitrogen testing. filling up the tubes with nitrogen and checking for leakage after blocking both ends. You can talk to ac guys regarding the same.

No advice, just sympathies.

Even with a coloured tracer, it's almost impossible to detect micro-leaks such as yours. The leak probably happens when ambient temperature inside the engine bay goes beyond a certain point.

For a start - the condenser and evaporator are easy to check for micro-leaks under water with nitrogen at high pressure. Then ask your AC person to replace the AC compressor seals (if that can be done - I am not familiar with the Forester's AC system). Next step, replace every single bit of tubing and joint, and the evaporator bottle (if present). Final job would be to replace the AC compressor itself.

This is becoming too expensive. Is selling the car an option? :)

Yes, I may just consider that. There are other issues cropping up (posted on another thread)

you should do a leak test on two units and its joints by completely removing it.
1. condenser
2. cooling coil.

The colouring agent what you have mentioned is UV dye. This needs to be purged into the system along with the refrigerant gas during filling. A very small amount of about 8-10gms of UV dye is filled along with the gas and fresh oil during the AC service. A minimum of 8 hours of a/c running later, the UV dye would have adhered to the every surface of the system. In case of leak the UV dye oozes out along with the gas. The point of leak is detected by running a UV torch over the entire system. A florescent glow would result in area of leak.
This dye is normally not available in all the workshops, check out where some high end cars are serviced.

Guna,

I suspect your evaporator coill has developed a leak.

Please have the refrigerant evacuated and then have a pressure test done at 350psig.

If you see no drop in pressure after,say,1 hr , it is worthwhile to have the evaporator coil removed(dash might need to be opened up) and tested separately - in fact even if you look at the evaporator coil and find traces of refrigerant oil , this is a tell-tale sign of a leak.

You could refer to my thread on my travails with my Corolla for more insight.

http://www.team-bhp.com/forum/techni...teps-pics.html