Do you mean a W211, 211.008 car or a W210? On a W211 it would be a separate
element in the heater core. But you mention the switch next to the cigarette
lighter, then I guess you actually mean a W210 or an S210 car.
Later models of W210 do have an electrical heater booster but this one is a
device at the engine bay, connected to heater water pipes. Don't know good
references but it is part number 240 in this parts diagram:
Note that this car would also have a water cooled alternator, meaning the
alternator also warms up the cooling water initially.
It is a W210.
And the picture is correct.
I have red someplace that this autostarts (no red light in switch) at about
below +5 degrees C. outside temp and watertemp below 40 degrees or
But it does not get hot. Fuse is OK.
I am able to read wiring diagrams but I do not have any.
I've seen higher figures for the engine temperature but this could have been
for the diesel based booster.
Which fuse did you check actually? I believe it is only protected by some
huge pre-fuse, the W211 electric heater is either 1600 or 1700 W!
You mean the heater booster unit does not appear to get hot? Ideally it
should not get too much warmer than the coolant but it should get warm even
if it was not operating, when the engine and coolant gest warm/hot.
If you have a clamp ammeter, you could measure the current on the 16 mm2
wire. I don't think there is any access to the switched wire, you cannot
measure it then with a multimeter in voltage mode.
I would suggest checking the thermostat too if the car does not warm up well
even after a longer trip. The CDI would be slow to warm up even with the
electric booster but it should reach normal temp if the thermostat is
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