Automotive Air Conditioning Information Forum

Hello everyone,

I have a Mercedes Benz GLK350 4Matic which is blowing perfectly cold air when I first start it up in the AM but once I turn the vehicle off it stops working. It will work fine again after a few hours of the vehicle being off. I have taken it to the dealership they recharged the system and it is still doing the same thing. They said it didn't have any leaks. I drove it non-stop (didn't turn the car off) out of state a while ago and the A/C was fine the whole trip. If I go into a store or something for a few minutes after turning the car off and come back it blows hot air and won't blow cold again until it sits a few hours. It also seems to blow hotter on the passenger side after I turn it off. Anyone have similar issues? Thanks in advance!

Classic symptom of a wide clutch air gap. When cold the coil can pull in the clutch driver, but once warmed up, the resistance is too great and that worn driver cannot be drawn magnetically across that wide gap. You need to remove a shim from behind the driver, remove the bolt, wiggle off the driver from the splined shaft, and drop out the widest shim- throw it over your shoulder and re-install driver. and bolt. and be happy.

I am surprised mercedes dealers don't realize or understand this very, very common failure mode-- your description is exact.....

You can test the wide gap by giving the clutch face a tap with a hammer handle when the engine is running.

The tap will move the clutch just far enough for the electomagnet to take over.