Excessive cabin heat temperature
 

Owner of a '97 W210 with excessive cabin heat coming from drivers side area somewhere when no A/C is on. We constantly have to be running the A/C in order to keep the temp down to a comfortable level. Can't seem to identify the source while driving.

Anybody have any ideas??

'97 W210 420 !!!!!

The duovalve could have failed. This regulates the flow of hot coolant to the heater.

Wouldn't this duovalve failure trigger the check engine light to come on? We have no such indicator.

Not a check-engine light, but there could be some indications available by running the diagnostics on the climate control module. See this site for how-to:
http://www.eclassbenz.com/node/27

Possibly a stuck open air flap, too.

I have not done a diagnostic check as I will have to wait for the weekend to do this.

The problem seems to come from the feet or shin of the legs area and seems to be more prevalent when the care reaches operating temperature. Can't seem to identify when I am driving the car!

Found the problem.

It was a torn steering shaft boot located on the fire wall. It look like it was a real problem to replace so I just used some HVAC aluminum tape to cover the boot. Works great, now I can roll the window down without feeling like the heater is on.

Thanks for all the support guys!!