Aircon one day, none the next

[Omega]

Hi folks,

Wonder if I can get some feedback/advice on a strange problem I'm having with the aircon/climatronic in our 07 Jetta FSI. The aircon has worked flawlessly for the past three years and then a few weeks ago the aircon stopped blowing cold air.

A few days later I took the car to the dealer (extended warranty!) and an hour later they called me to advise the aircon was working again but they couldn't find any faults. As they couldn't find anything wrong they kept the car for two days to give it a thorough going-over as the problem baffled them. Despite testing, resetting/re-gassing they still found no faults (and no fault codes).

Yesterday the aircon stopped blowing cold air again - same problem as before. I left the car for a couple of hours and then had a fiddle with the diagnostics function on the climatronic to see if I could see what rpm the compressor was running at as it was still engaging even when the aircon wasn't blowing cold air. Apart from fiddling with the diagnostics I did nothing else, and hey presto the aircon started to work properly again.

I'm wondering whether using the climatroninc diagnostic function resets the aircon or something to make it work again? It's just weird that the aircon, on two separate occasions, starts to work again after using the diagnostics - the dealer probably initially did diagnostics too which may have caused the aircon to work again when they first checked the car.

Any ideas?

[DNA Tuning]

I would get them to check all relays and fuses as well (ie. replace them) as the problem definitely sounds like an electronics issue.

Failing relays have a tendency to start switching intermittently before completely failing to work. Fortunately they are generally "cheap" components.

[Jmac]

I would be checking the cooling fans are cutting in the minute you turn on the AC. If not thats the problem. The cooling fans run to lower the temp thus lower the pressure, as pressure and temp are related. There is high pressure/low pressure switch keeping an eye on the pressure, too high because the pressure is too high, then no AC cooling
If they are reading with diagnostic software are they checking the live data?? looking for fault codes isnt the answer
Keeping hold of the car for a bit till it fails helps, intermittant faults are a real bind, if its all working its hard, you have to start wiggling bits and bobs, same as dead on arrival cars, MY FAVORITE

Cheers
Jmac

[Omega]

are they checking the live data??

I hope so. They told me they had to send some data to the techo's at VW Aus. who then advised the dealer to reset some settings to factory defaults.

I'm leaning toward it being some kind of electrical issue, but surely wouldn't one of the first things they would have checked the first time was the fuses and relays? Those are the first things I checked when the aircon failed the first time - but I couldn't really check the relay other than taking it out, giving it a few taps and sticking it back in.

The thing is I don't want to keep taking the car back to the dealer (with the aircon working again when I take it there) for them to just perform checks on a working system and find no faults.

[Jmac]

Yep thats right, its way easier when its failing for sure for all. If it fails for you pre dealer check, check your fans are on mate
cheers
Jmac

[Omega]

check your fans are on mate

I'm guessing that's the fans in front of the radiator?

[Jmac]

Thats correct

[Guest0608]

I have seen a jetta abit like this one..........For a start the a/c compressor is AWAYS running even with the A/C is switched OFF on a mk5/6 at a certain % to keep it all nice and not seizing up over winter when its not used (OK, you say what winter in QLD! hahha) so looking at the actual compressor doesnt really help these days unless it torn itself apart! The OPS unit can turn the compressor OFF if it see's the battery voltage has dropped below a certain voltage.....the one I saw did this about once every 3 weeks! but the problem was the battery voltage wasn't dropping just the OPS unit thought it was..... connection poor on a main battery wire.......... keep a eye on your fault codes for "battery voltage intervention" if you see that then this could have been a possible cause.........vwtech

[triode12]

I have seen a jetta abit like this one..........For a start the a/c compressor is AWAYS running even with the A/C is switched OFF on a mk5/6 at a certain % to keep it all nice and not seizing up over winter when its not used (OK, you say what winter in QLD! hahha) so looking at the actual compressor doesnt really help these days unless it torn itself apart! The OPS unit can turn the compressor OFF if it see's the battery voltage has dropped below a certain voltage.....the one I saw did this about once every 3 weeks! but the problem was the battery voltage wasn't dropping just the OPS unit thought it was..... connection poor on a main battery wire.......... keep a eye on your fault codes for "battery voltage intervention" if you see that then this could have been a possible cause.........vwtech

Sorry for the stupid qn - but what does OPS stand for?

[Guest0608]

OPS = onboard power supply but vw have many different names apart from OPS, they keep changing them but its the same thing, basically the ecu that monitors the car etc.............vwtech

[triode12]

OPS = onboard power supply but vw have many different names apart from OPS, they keep changing them but its the same thing, basically the ecu that monitors the car etc.............vwtech

Ah! Thanks for that.

[Omega]

Hi folks,
Just a quick update on my intermittent aircon problem. It was working fine since my initial post a few weeks back, but today whilst out doing the grocery shopping, I went to start the car and it sort of hesitated but started and it made a very strange noise, very much like loud tappets (or similar sound to a piece of paper being poked into a electric cooling fan), the tappet sound got faster when engine was revved. And you guessed it, no aircon again.

I took the car to dealer straight away and they had a quick look and advised that the compressor had died Now they have to order in a new compressor, condenser etc but they couldn't give me an eta. This is a real bummer because we had a road trip planned for next week to take my 3yo to her grannies 80th - it's an 8 hour drive and without aircon it's too risky with a child onboard. How long would these parts normally take to get in - surely compressors and the like would be held on-hand for dealers to order up overnight? And assuming parts are available, how long would it take to replace compressor, condenser etc - 1 day, 2 days?

Thanks for any replies.

[Omega]

Oh and I forgot to mention, the dealer disengaged the clutch mechanism on the compressor so as not to cause any damage. Since they did that the engine sounds normal again, ie no loud tappety sound. So that noise was obviously from the compressor chewing itself up.