Car: 95 E300D
My fuel gauge has been jumping around for over a year now. I didn't expect cleaning the fuel sender to help (it didn't) since the nichrome was badly kinked in several places. I got a used fuel sender for $20 and cleaned it thoroughly before installing it to no avail. I tested the resistance on both senders moving the float slowly up and down. The old one failed miserably, but the (old) new one functioned properly after I cleaned it, yet the fuel gauge still jumps around.

At this point I'm looking for other causes. There is a copper fuse on the back of the instrument cluster. It looks fine, but I'm not sure of the amperage, or if it's even relevant. A few minutes ago I removed the oil pressure/fuel/temp gauges from my instrument cluster but I don't see anything that is obviously wrong. This thread mentions soldering the fuel gauge connection points, but I'd rather not have my gauge soldered if it turns out to be something else and I have to remove it again. If it's a bad ground connection as the above thread also suggests, how would I test for that? I also have the DVD which states the only cause of an erratic fuel gauge to be "cold solder joints on the resistance bridge for fuel gauge" remedied by resoldering the resistance bridge. I have no idea what a resistance bridge is, or where it would be.

The same page I am quoting from also says I can request "precise working instructions" by sending a fax to 0711/1763454. 0711, I think, is the area code for Stuttgart. I don't have access to a fax machine right now, so if anyone is interested, I'll pay for the long distance (paypal?) if you can get those instructions. Of course, you would have to dial 011 (us exit code) and 49 (Germanys country code) first. If there are no takers or otherwise, can someone point me in the right direction here?

Well I don't have the specific info you want, but I am an electronics guy so I am drawn to these threads like a moth to a flame... And speaking of of flame, be very careful working around the fuel vapors with the electrical sender!!

Anyway, I would suggest this test be CAREFULLY done: Remove the sender from the tank (I hope this is not too difficult). Seal up the hole in the tank so there are no fumes around. Hook up the sender and put it in some different positions and see if the guage reads right. My theory is that the sender is actually intermittant. Now I know you said you tested it, but I am wondering if the pressure of the wiper on the nichrome element is as good as you think. I know on other cars I have had, the wiper wears, and the wire wears and it can be hard to correct this. This is all just my .02. Good luck.

__________________
1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

I just put the cluster back together and drove around for a while. So far, with a nearly empty tank (which usually provides the largest inaccuracies), the gauge has been pretty accurate. This gives me some hope, only because up until now, the gauge would jump around almost constantly. Now I'm thinking that maybe there was a bad connection between the gauge and the circuit board. If it starts acting up again I'll do that test with the sender. Thanks for the tip.

I send a fax to that number in germany (free internet fax service), i don't have a way to receive a fax so i told them to send it to my email (it might be one of those fax-on-demand things where they automatically send the instructions back to the number it came from; in that case you're SOL)...i'll let you know if i get a email from them in a day or so....

toodles