weird electrical problem speedometer

[chamilun]

I have a speedometer that only goes to about 60 when the engine is warmed & restarted, or so I thought.

Apparently, with the headlights on, turning the knob to the left to dim the lights causes the speeometer to slow down, and turning to the right allows it to read correctly.

Another oddity: it seemed when I turned the knob to the left, the a/c didn't cool as well.

Is this a ground problem of some sort?

[dshepp806]

What year car?

Could be ground issues,..could be some funky wiring....one would have to study the Bentley prints to discern.

This is a first, as I've not heard of this symptom...may be a good one when you find it.

Have you a Bentley print?

Best,

Doyle

[chamilun]

sorry,
1982 911 sc.

I do have the Bentley manual. Will begin looking at diagrams soon.

[pete3799]

First off .........what are we working on here(year)
If you have a Bentley manual i would spend some time checking the wiring diagrams.
You've got some wires crossed some where (possibly on the back of the spedo).
have you had the spedo or ign. switch out recently?

[chamilun]

solved!

turns out the ground connection had come off.