hey there, my 97 s500 coupe only blows air out of the side and dash vents. both center vents and floor vents are dead. and so is the heat. this happened all of a sudden. i'm sure this is a common issue, does anyone know which part i have to change and where it is located? my guess is electrical under the dash accessible from under the hood..... thanks in advance.

 

come on guys...

 

I'll try to help but I don't have any real experience on MB heater units. I've never had a problem!
The vents are opened /shut by motorised valves attached to the "heater" casing behind the dash INSIDE the car. Sometimes pneumatic (vac) and on other models electric.
Since some vents appear to operate and others not I guess you have a vent valve (motor) burnt out or vac tubing perished/disconnected since they are not (to the best of my limited knowledge on this subject) individually fused. However the outboard vents may not have any electric/vac controlled valves on them, only manual thumbwheel valve.

Is the blower motor working OK? You indicate that it is.
Can you change air from Cold to Hot etc? i.e. is control unit working.

I assume you are talking lack of airflow rather than lack of "Heat" / "Cold" which is an entirely different fault.

Stuart.

 

it's both. blower is good. heater doesn't work. ac is good. center vents are dead. red lights turn on when i press the buttons to activate the center vents though. so it's a lack of airflow as well as a heat/cold issue and they happened at the same time.

 

theres a unit in the engine compartment that somtimes siezes up , try oiling it to free it up.