petrenk01

Hi guy, on my 09 GL450 after freezing weather began the heater worked fine but then a few weeks later it just stopped working. at first I thought it might be a sensor got frozen, but now it got much wormer, not freezing at all but heater still works only occasionally, when ever it chose to.
and I don't know where to look for the issue.
any body have any ideas or experience?
thanks

alx

It could be many things, but it is most likely the fan computer.

Mercedes in their infinite wisdom stuck a large part of the hvac computer in the front fan housing. No, it is not a final stage resistor pack, but a full blown computer. Unfortunately they also forgot to make it water tight and moisture from the fan flow seeps right around the fan axle and into the circuit board area. This results in the computer getting wet, misbehaving (usually likes to stay on after the vehicle is turned off) and eventually burning out altogether. The computer is potted in epoxy, but this only delays the failure.

There is no replacement circuit board and the whole fan assembly needs to be replaced.

this is a very very common problem as there is a design flaw that unless you live in a dry place like Arizona will always manifest itself after few years.

petrenk01

sound like I have a good chance that my warranty may cover it.
thanks for reply that was very helpful.