Weird heater problem W126
 

Hello all,

My 300SDL climate control functions properly in summer and winter, but I've noticed something wierd that it does.

In the middle of winter (today was 9 degrees Fahrenheit), I get a cold draft from under the dash on the driver's side. The footwell flap seems to be working, as some hot air comes out near my feet, but there is a distinct blowing of cold air also.

While in the drivers seat, I can feel cold air primarily in two places:
1 - Near my toes at the top of the accelerator pedal. My toes go numb after driving for 45 mins in cold weather. Rest of car is comfortable
2 - There is a distinct blowing of cold air between the steering column and underdash panel. The underdash panel I am referring to is the one that has a change tray on each side of the steering wheel. There is a "curved" section in the centre of this panel where it mates with the steering column and there is an air draft from there.

Some observations:
-Happens at any speed. Doesn't seem to be an exterior air leak, since it happens even at idle.
-Something is definately moving the air. It's as if there is a fan under there blowing cold air at me.
-Changes with fan speed. Lower fan speed=less cold air. If I turn the fan off, no cold air blows (no heat either :eek: )
-Operation of system seems fine otherwise. The defrost works, center vents work depending on the setting, footwell flap opens & closes as it should, etc.

Any thoughts? I'm freezing!

Oh, and everyone try your best to refrain from commenting on my stupidity for living where it's 9 degrees in mid-afternoon on a sunny day :sun_smile

Thanks!
Neal

Hot air in driver's footwell should come from slots, about 3-4" long where the hard plastic and the carpeted sections meet under the dash. Mine had no air from slots, while passenger side had air.

The only cold air with fan power should be the center console to the rear venetian blind in the center, cold air whether cooling or heating. This is usually shut off for rear seat passenger comfort, but if the plenum is leaking, it could be the source for your cold air.

You could try removing the under-dash panels, 3 philips screws under the pry-off covers at the back of the tray, then 2 or 3 (I don't know, mine has 2 remaining) 1/4 turn large plastic fittings, they look like screws but only turn the 1/4 turn to release and 1/4 turn to lock. With the panels out of the way, maybe you can see/feel for the soruce of the air.

Best Regards,
jim