EWT

The air conditioner on my 08 GL550 has started shutting down occasionally. It still blows, but doesn't cool. Turning the system on and off sometimes will fix it, and other times it just comes back on by itself after 10-15 minutes. When the system is turned on and off, the compressor seems to work for a second or two (you can feel the air starting to cool) before the fan hiccups a little and cooling stops. I had the compressor replaced at the dealer last summer when it failed. When it started acting up (about a year after the compressor install), the dealer evacuated the system, found it had lost a little R134, refilled to the correct amount, checked a ground on the compressor and proclaimed it fixed. It wasn't working again when I came to pick it up so they flashed newer firmware onto the HVAC controller. This time it worked when I picked it up, but it has stopped working several times since then.

It seems to occur more on hot (100F+) days, although it has happened on cooler days too and doesn't have any issues on some days. The problem only happens after car has been driven for a little while. It never fails to work when the car is first started, and when it is working, it cools really well.

Any guesses what might be going on? Faulty pressure switch? Bad electrical connection somewhere? Thanks for any help - driving around in our recent 105F+ weather without A/C isn't pleasant.

Avdoc

My GL550 acted like it was getting a heat soaked condenser after sitting in car line picking up kids on hot days. It would be great ten after 10-15 min it would slowly turn to just a vent and no A/C. After we would drive and air would blow over the condenser it would cool down. I took it to a mechanic and he found zero codes, so he just did a full A/C service on it and it was a little low on freon. It's cold now, even though I may have to turn the fan up a click or two when sitting a while I still get cold air.

You may just need to have it serviced to see if it's a little low on freon

mefferso

When mine had similar symptoms, replacing the a/c compressor fixed it.

EWT

Thanks for replies. The compressor was replaced last year, so hopefully that shouldn't be the problem although I also had similar symptoms before the compressor locked up. It was also making some noise, which I'm not hearing this time. I thought it was an idler or tension pulley and had the parts on my workbench waiting. FYI, a seized compressor means you need a flatbed since it will take the serpentine belt out with it. Having a dead vehicle while taking your son and 4 friends to an out of town waterpark isn't pleasant. AMHIK.

I had a similar problem on a previous car with the A/C cutting out on hot days while parked (I think the system was slightly overfilled), but this happens at any speed. I'm going to take it back in and see if the dealer has any other ideas, but since the problem can't be reliably reproduced (has worked fine for 5+ days now), it is hard to diagnose/fix.