Westwind

Hi,
My 550 is about 7K old.
Was coming back from a trip yesterday. Had my AC on at about 70, 'zone' turned on so both sides were equal. For some reason, my side started blowing hot air. I mean, heating like its 20 degrees inside. So I checked the vents on passenger side, and they were blowing nice cool air. I turned 'zone' off, and dropped mine to 65, and even lower. No change. I tried all kinds of things - Turned 'auto' on. Turned it off. Tried different 'modes'. Whatever. It would not obey any commands. I was sweating bullets here.

Finally, I pulled over. Turned the car off. Let it sit for a few minutes. Turned it back on. Life was good finally. Its working fine now.

Its not an issue anymore, but just wanted to share and see if anyone had any technical insights. If not, its no big deal. I just hope it does not happen. If it does to any of you, you know what to do.

HBerman

I had a similar problem with my 2011 E550 when it had less than 750 miles on the clock last year. The only thing that restored the system to proper function was to turn the car off and to wait 5 minutes unitl everything quiesced. I reported this to my dealer, but they could find nothing wrong and there were no codes logged to inidcate the malfunction. It's never happened again in the last 10 months and 12,000 miles. My service advisor speculated that the system has lost communication with the sensor on the driver's side of the car and thought that it was way below freezing so that it needed to turn on the heat!!

konigstiger

Depending on build date dealer may need to flash AC software reference bulletin LI83.00-P-050296 https://mbworld.org/forums/4342943-post20.html

Westwind

Thanks for the details. Now I have something to show them. Normally on these kind of rare incidents they just scratch their head, ask you to go home and hope it does not happen again.