My newly acquired 300TD has some strange electrical gremlins - like, when I put the head or side lights or indicators on, the fuel gage goes to 100%. Anyway, I substituted my spare instrument cluster {from a 200TE} and the problem disapears - turns out I have two burnt tracks on the board that supports the fuel gage, oil pressure & coolant temperature - both tracks are the earth return tracks.

So, I consider repair or just substitute - whilst examining the spare cluster I find that too has two burnt tracks - but this time different tracks - one track each side of the rhoestat that powers the dashboard lamps.

So, am I just unlucky or is this a weak spot in these cars?

I'm not sure how exactly I'm going to proceed here - it is possible that I damaged my spare trying it asa substitute in the car - so I'm going to work thru all the 15 pins on that rear connector and see if I have any ground faults which could explain the large current draw - any advice welcomethough.
STeve

I just repaired a couple of burned console lighting tracks on the instrument cluster board of my '85 300TD. The short took out the rheostat after the repair (soldered in wires to bridge the tracks). Mine was an intermittent short; turned out to be the wires going to the back door window switches. These switches are lighted through the rheostat, but only light up when the rear window switches are "armed" through the console safety switch. Repairing the wire bundle from the pillar to the back door took a while.

The burned tracks supplying ground to the fuel gauge, etc. probably resulted from a shorted sending unit or associated wiring.

The fuses should protect the wiring, and blow before any wires burn. But the tracks on the circuit board are much smaller than the associated wires in the same circuit, so they burn before the fuse opens. Substitute a wire for the burned track, and the fuse will open. Then find the short!

V-P
Five M-B diesels, last count. And a VW Rabbit diesel, and an Isuzu TD. Gotta find a new hobby.

__________________
Dale
'67 Volvo 122
'79 Rabbit Diesel
'79 M-B 300TD
'82 M-B 300D
'83 M-B 300CD
'85 M-B 300TD
'86 Isuzu P'up TD
and a couple of Hondas