1999 Mercedes Benz S500 Fan/Heater problem

MLUBIENSKI

MEMBER
1999 MERCEDES BENZ S500
V8
2WD
AUTOMATIC
100,000 MILES

Recently my fan/blower failed but yesterday, driving in subzero cold I tried my front defrost and suddenly started getting hot air up front. Great but one problem-the controls had no effect on fan speed and when I stopped and took the key out of the ignition the hot air continued. I've removed most of the fuses but the only way I've found to stop this air circulation is to disconnect the battery. The area where the air seems to be arising is just in front of the middle of the front windshield. Any suggestions?

1 Reply

GFIMOTORCARS

MECHANIC
673 POSTS

If your heater is only blowing on one speed and through one set of vents you are more than likely looking at a failed AC pushbutton control panel/unit. A fancy name for the buttons and switches you use to control your AC and heater and where it blows and how hard. When this fails it often is stuck to a position and speed no matter what you select. If you are only experiencing the fan working on one speed (not the same through all speeds) then you are experiencing a failed blower motor resistor.