Fuel Level Sensor Problem
 

Does anyone have a drawing and/or schematic for the fuel level sensor used in a 1973 220D. Mine has stopped working. The rod that the float rides on has rotted away near the bottom of the assembly making it come free from the outter can. The wire that receives the 12 volts is just hanging loose and the wire that runs up and down both sides of the float is just hanging loose. I have access to plenty of equipment to make repairs to it, but I need to know exactly how the wiring is supposed to be hooked up in the can. Any and all help would be greatly appreciated.

If it is anything like our '91 190E - and that could be a stretch - the float contains cross-contacts that ride the wires and short across them. One wire is a resistance element, the other has no resistance. Measuring across the pins the wires attach to at the top, you get a variable resistance that is low when the float is high, and about 75 Ohms with the float bottomed out. Also, the slide shaft is attached to a third pin up top, and at the bottom cap to an electrical contact. Another electrical contact down there is attached to the 0 Ohm wire. A copper plate on the bottom of the float shorts the two together, completing a circuit that signals the 'reserve' light to come on.

Now, I doubt it makes sense to repair the sort of damage you are describing, unless it is impossible to find a good replacement part. But, if it is your only option, I hope this is of some use.

Steve

Thanks Steve, this should help me at least get started. It's tough driving a car with no gas gauge and no odometer.

Bob