I posted a few weeks ago about my fuel gauge not working right on my W124. It jumps around a bit sometimes. It'll show you have 1/2 tank, then suddenly only 1/8 tank.

Someone said that's an indicator sludge is getting on the float device in the tank so I took that out it was in great shape, no real sludge on their to speak of. I took it apart, cleaned it up real well all over including the electrical contact points, put it back in and....same problem.

Any suggestions? Maybe it's simply toast. Is there any way to repair these or just buy a new one?

1991 300d, 230k

How did you clean it? Did you take it all the way apart? The wires build up an insulating layer and stop conducting. The only way to get it cleaned is to *GENTLY* clean the wires with steel wool or very fine sandpaper. It also helps to *EVEN MORE GENTLY* run a piece of very fine sandpaper (1000+ grit) under the faces of the wipers that ride on the wires.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Could it be cleaned in an ultrasonic bath???

Anybody,

__________________
"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Disassembly and mechanically cleaning the sender is about the only reliable way to clean the crap off and get it working right. The buildup on the wires is usually such that no amount of solvent or ultrasonic massaging is going to do a satisfactory job.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

There is a choke on the side of the gauge that stabilizes it's motion. The choke is a coil of wire wound around a plastic spool. If the spool breaks, the wire will intermittently short to the case. See this post for photos and information:

https://www.peachparts.com/shopforum/diesel-discussion/394040-solutions-some-odd-dashpod-problems.html#3

All you need to do is pull the instrument pod and insulate the coil from the case. You can do this with shrink wrap or electrical tape.

when you disassembled and cleaned the gauge sender, did you take a 3M pad and polish the two fine wires that form the basis of the traveling resistor? they need to be bright and gunk free as well as the sliding contacts that ride on these wires. as you may know, they are extremely fragile. the third middle wire is simply a ground wire to the bottom of the sender for the contacts on the low fuel light.
-dan

Ok, I got it.

Had my mechanic come by. He noted that one of the fine metal strands had jumped out of the place where it's supposed to be. That was probably due to me cleaning it the week before, I must have accidentally got that wire to move out of place.

The wire's back in and all is well.