W114 Fuel gauge always showing past full??
 

Hi guys, I know it is common for the sender to be the main issue with the fuel gauge not showing the right amount of fuel but in this case I am confused? I have read the other posts inc the DIY and tried it all (earth, clean sender etc) but no luck.

The strange thing is that when I unplug the three point connector in the trunk the gauge does not respond still showing well past full, when I turn off the car it falls back down.

My question is shouldn't the gauge fall if I unplug the sender (in the trunk??) what is providing it with power to move all the way past full?? I unplug the connector and no change in the gauge :confused: any help or tips re what to look for or try next?? Note the other gauges work fine its just the fuel gauge thats driving me crazy:( (ps found out the hard way it was not full ..

...forgot to mention low fuel warning lamp does light up
 

Guys not sure if important but the orange low fuel warning lamp does work after I cleaned the sender it now lights up its just that the fuel gauge shows its full (well its well over past the full tick) can I assume the gauge is faulty????

Thanks BI

sounds like you might have a ground issue, and or faulty gauge and or sender (sorry):o You have to rule out each one
Let start with the unit in the tank.
I take it from your post you have had the gauge out of the tank. Did you test it with an Ohm meter?
when you slide the pod you should get a change in resistance. when bottomed out you should get continuity, off the bottom - open

Take it out and inspect...as Meltedpanda suggested,check the resistance values,which should be:
4,7 ± 0,4 Ohm full
65,7 ±1,4 Ohm tank empty.
I`m pretty sure yours is the same on w110 fintail models(as well as many others),MB Number A1105421204=VDO 224-817-001-014R
http://www.epsparts.com/product/1105421204/MERCEDES_PARTS_GENUINE_FUEL_TANK_FLOAT_MOST_1963__1975.html
http://www.kienzle.de/uploads/media/sensoren_instrumentierung.pdf
130-140$$.I had no luck at junkyards,all 3 were shot...

I actually rebuilt a few , need NiChrome wire and a steady hand, but it can be done

update...
 

guys thanks for the input made the ohm check and it pointed to the gauge, the sender was good, will pop a new one in, thanks again for the ohm numbers :-)

You sure it's the gauge and not a short in the wires making it think the tank is full?

Remember, it's supposed to be 0.4 ohms full, and you're showing >full which would sound like 0 ohms of resistance... which is a short.

Hi tomguy did another check and your right not sure how I got the diff readings, ....ok so decided to check for a short, after tracing the wires thru from the sender I think I found it at a junction point at the front of the car under the glove box, touched the wires and the gauge worked, I think it might be corrosion?? will pull out and clean up..thanks heaps tomguy ;)