Date registered: Sep 2012
Vehicle: 300sel W109, 280S 70 , 220s 62. 230 66. Lancia Flavia 63.Pininfarina
Location: Totteridge London.
Mentioned: 0 Post(s)
Quoted: 59 Post(s)
The three contacts on the sender are ground, reserve light (switch that closes a connection to ground for the light to illuminate) and the float contact, which essentially provides the gauge with a variable resistance in its ground circuit.
Grounding the sender wires ignition on- one will light up the reserve light. The second one will send the fuel gauge to full and the third is itself ground.
the sending unit resistance wire has a resistance difference of only a few ohms from min to max .forgotten figures now but can check if required .