speedometer problem

[greezsmnky]

Hi i was wondering anyone know why my speedometer goes up to like around 60-70 mph when i rev the tach up, the speedometer goes up with it. But when i unhook the speed sensor on the tailshaft the tach is fine. And the speedometer is still. This is on my 1988 lincoln lsc mark VII. None digital dash.

 

[LuxurySportCoupe]

Sounds like you have a bad ground.

 

[NYC LS8]

Either you need to ground the orange wire behind the speedo cluster or it's a bad alternator.

 

[greezsmnky]

Either you need to ground the orange wire behind the speedo cluster or it's a bad alternator.

Thanks for the advice the alternator was bad, put new one on solved problem.