ht800

Hi, I am new on this forum. I bought new 2011 ML350 4Matic 2 years ago, we did not use the rear site heating until a few weeks ago, and kids complaining the cold air is blowing to their face. The air is blowing from vent of the armrest section between front seats, we tried to use auto heating or manual heating (max fan, auto off, A/C off). but it keeps blowing cold air even after long time. We sent to dealer as it is still within warranty period, they told me it is step motor problem, and order the new step motor, installed the new one. I was happy it got resolved, however when I drove it home, and try again, it behaves same as before. It only blows cold air no matter how you change the two zone temperature control. I am really frustrated, and plan to take it back to dealer for checking tomorrow.

Does any one has the same issue?

Thanks,
Ht

xxGenericSNxx

Do you have 2 or 3 zone climate? (I know you mentioned the two zone in the second to last sentence, but I just want to double check)

Are you sure the unit ever blew warm air to begin with? While this won't help answer your question, an anecdote I have is that on the W140 S-Class (the 90s era S Class) if the vehicle only has 2 zone climate, the rear vents simply act as a vent and only has cool air coming out of it, regardless if the heat is on in the front or not. I'm not saying this is going to be the same with your car, but it's possible it is.

ht800

My ML350 is two zone. Yes, it never blew warm air at all, (on the contrary) instead it blows cold air always from the vent between the two front seats. I tried one of my friend's R320, and they have warm air blowing from the vent, they have also button beside the vents to allow to blow towards to face or legs, where mine does no thave those buttons.

I wonder if anyone has ML350 ever used the warm air in the second zone? That shoudlbe a popular models, and in winter I would imagine people will use that very often.

xxGenericSNxx

I wonder if I may have a similar issue as you. My R has the three zone climate control but the vents in the center console don't seem to blow warm air while the B pillar and third row vents are fine.

ht800

I went to check my friend's R320, and the middle vent console does blow the hot air. So sound s like your is not functioning.

ht800

I took the ml350 to the dealer, they could not figure what could be wrong after 3 or 4 technicians look into this. They conclude the issue mus be the front panel controller, so they are going to order a new front panel - the whole piece and replace it. For my car, the floor vents under the two front seat could not blow the hot air, it only blow the cold air. It is not easy for people to notice it unless you really pay attention.

xxGenericSNxx

At least you're under warranty!

BTW when my rear AC compressor (for the third zone) went out, my tech told me there was so little information that he could get on it from MB itself. The info was buried deep in one of the sources that they use. So perhaps the info is out there, but just hard to get.