why is the heater on my mercedes 220 D hot when switched off?
No fuses are blown, there is a 12 volt supply to the common connection of the two water valves, the valves work when either or both are connected to ground but the light does not work on the recirculation switch and the air flap does not work.

No air conditioning is fitted to this model a very basic three switch heater control panel is fitted, the fan speed is working, the heat switch and recirculation switches do not do anything.

peter, June 2008

Hi Peter, most heater valves default to the hot setting, and as you have proved that the valves operate when a ground is put on them it only leaves the control pane or the wiring in between, I have copies of the wiring diagrams if you need them
nige110162@hotmail.co.uk

nigel, June 2008