I am going to pull it and have a look once it warms up a bit here (zero F here tonight!). The wire was just installed so I can't see there being any wear. But something must be wrong!

The ground wire that has to be disconnected when the cluster is removed goes to that screw tab, so I figured it should be a good spot!

I was a bit puzzled as to why they needed a separate ground going through pin 15. But maybe that is the main ground and the one I used is just an additional one. Once I have it out, I will follow the traces and perhaps run the white wire to where it should have gone!

The temp gauge only seems to be grounded out in the engine bay. When key is turned on, it goes from zero to full scale.

Bill Hunter wrote in the DIY General forum:
"Field expedient upgrade:
On the rear of the fuel gauge circuit board there is a square tab (screw mounts through it) grounding the speedometer assembly.
Make/install a ground wire with two spade connectors in the center, mount it from the square ground point to a solid body ground.
This reduces/eliminates most instrument cluster electrical issues.
The spade connectors in the center of the home made ground wire are for easy instrument cluster removal in the future."

Seems to imply that that tab is a good ground point.

__________________
Graham
85 300D,72 350SL, 98 E320, Outback 2.5