Fuel gauge does not work - low fuel warning works

[Benjegen]

Hi,
On my 250SL the red warning lamp for low fuel is working, however the fuel gauge shows absolutely empty irrespective if the tank is full or not. Did I understand that right from the other threads that in this case the sender unit is OK and the problem must be somewhere in the gauge itself or the connection to the sender unit ?
Thanks !
Ben

[hauser]

I replaced the sending unit and the problem was solved.

1969 280sl 5 spd
Gainesville, Fl.

[Ricardo]

Ben
Try taking the sending unit apart...it's a pretty simple affair and easily disassembled. The unit works by use of a fine resistor wire that has a float making contact with the strand which loops down and back up the other side. The strand of wire may be broken and this can be a little difficult to replace, not so much due to it's placement but to the difficulty finding resistor wire with a .5 ohm per foot resistance. Or the unit may just be gunked up. There is a little maze affair on the bottom of the sender which slows the escape of fuel to prevent your gauge moving with twist and turns in the road. It gets plugged with fine sediment and can cause some erratic readings, though not likely complete failure. Still it's worth checking out as it is another fine example of the unique engineering of Mercedes and kind of cool to see how it works.
Richard