2011 GL550 AC Blows warm on driver side only
 

Strange problem started about two weeks ago, brushed it off at first, but it's getting hotter. Now its becoming uncomfortable to drive. Anyway, it's a 2011 Gl 550 with rear a/c. The passenger side vent and rear air is cold. I took a temp reading at the vents and got the following:

Outside temp: 94
Driver vent: 85
Passenger side vent: 71
Rear a/c: 72

I do have a iCarsoft scanner, I checked for any faults and they were no stored or active codes. I also viewed the actual value data of the left and right blend door. Both of the actual values match the output values of the climate control. I do hear it change position when putting the climate to hot and cold. I do see after searching that on other mercedes a low refrigerant charge causes similar problems, however I'm having a hard time believing that is the cause in my case. Has anyone had a similar problem on the 164 chassis? I am tempted to put my gauges on and add a little more freon just to see what happens. Any help or thoughts would be greatly appreciated!

Edit: forgot to add, the driver side DOES get cold randomly during longer periods of driving. But it will get hot again randomly as well.

Don't be foolish and add anything until you determine that is what the gauges indicate-----an alternative is find someone with factory diagnostics and the problem will be quickly found.

I had a similar issue of random side differential cooling except the passenger side cooled while drivers side was warm. Eventually it quite cooling all together and replacing the a/c compressor was the fix.

I have the same issue, it's my driver side that is blowing warm. I will be taking it to get a new rear sam coded, Ill have the see if theres any diagnostics they can run in STAR while they are there. Really hoping a A/C compressor is not in my near future. Time will tell.

If you find out it is the compressor and want to save some money, here's a writeup I did on the installation: https://mbworld.org/forums/gl-class-...ement-diy.html

It was about $450 in parts doing it myself.

in the W211 there is a switching valve that goes bad, and you will get hot air from the rear and cool air in front. is it possible this is the issue with the GL as well. I will do some research on where that valve is in the GL.

That would be much appreciated!

Looks like there is no duovalve on these. If there is I can't find any info on them.

Most likely low refrigerant due to some leak. Seals dry up over the course of years.

https://www.walmart.com/ip/A-C-Pro-P...ornia/36158903

Buy this recharge kit. Check pressure after turning on the AC on full blast. If it is in low range, recharge it. There might be a small leak. If it is in red range, DO NOT add refrigerant.

OR

take it to dealer or shop to properly diagnose it.

Thanks for the reply. In my original post I noted that I took the car to the dealer and they believe it is the evaporator. They also want $4,000 to fix it.

You have exactly described the same issue I’m experiencing with my 2008 GL450 - individual climate control for front plus rear ac. My intuition leads me to believe there is a random mechanical malfunction with a valve, damper, door.. etc. Any suggestions on what and where to check?

Usually a leaky evap in those trucks, yes. Left side is further away from the TXV so gets hot first. only seeing 20 degree cooler temps on pass side is not good anyway, should be close to 40 degree temp drop on a working system. Find a local a/c shop that will do the Evap cheaper.

On my 2009 GL550 this exact same scenario started today. 7/30/21 Did you ever reach a consensus from this thread for an answer that solved the problem? I just bought an ICarSoft ll 3rd generation scanner but haven’t had time this afternoon to hook it up.

As noted, there are a couple things that can cause this issue - which are all noted in the thread. Take a read through and check those things out. Checking out pressure at the hi-pressure fitting on the system is probably a good first step.

Then that's where I'll start. Thanks for our input.