85 911 no speedometer after changing fuses. Coincidence?

[cabmandone]

I had some rear tail light problems so I replaced all of my fuses. The tail light problem is solved but now the speedometer doesn't work. Could this be a bad coincidence or is there a fuse problem? I looked at my fuse panel and didn't see a speedometer fuse but I know they are electronic so there must be on right?

Any help is appreciated.

[E Sully]

You should have 12V on the back of the speedometer. I believe it is R/Bk from the front fuse block.
The power is picked up before the fuse, so it is not protected, and should be hot in run and start position.
The sensor for the speedometer is on the transmission and travells through the tunnel to the instrument cluster. The wires should be Brown and Green. They do not use voltage, but are triggered by magnets in the transmission.

[cabmandone]

Thanks! that gives me somewhere to start. It sounds like this is just a coincidence then that my speedo dropped out after changing fuses.

[porwolf]

I took a picture of the back of my original 1979SC Speedometer when I had the worm gear repaired. For the connections maybe this helps: