MoovnOn

The a/c on my 1998 C-280 works fine while the engine is idling or at a constant speed while cruising down the highway. However, if there is ANY load on the engine the blower speed decreases to low and different air vents open and close. In other words, if sitting at a traffic light and I touch the accelerator, this happens. As soon as I reach a constant speed and there's no load on the engine the blower goes back to high and the air coming from the vents returns to what I had when I was sitting at the traffic light. While cruising down an interstate, if I press the accelerator pedal this happens, and when I let off the accelerator everything returns to normal.

This seems like a vacuum problem to me, but I can't find any leaks anywhere and there are no other vacuum problems such as windows, trunk, etc. Using a code scanner, it shows no errors.

Any suggestions what could be causing this?

faithful_lothario

my car does the exact same thing. I think its normal though, or at least i thought it was until you said it could be classified as a problem.

MoovnOn

It isn't normal. I've had this car for six years and it never did this until recently.

MoovnOn

This problem has been fixed. It was a vacuum leak in one of the vacuum elements that operates the vent flaps. If anyone else is having similar problems, PM me and I'll try to provide some help regarding how to troubleshoot vacuum leaks.

ohlord

The climate control on 98 and up MB have a built in diagnostic program.Glad you solved the problem!Funny that with a vac leak it didn't throw a CEL.
ohlord
"GOT CODES?"