Does anyone know why my stock 69' speedometer gauge reads 100mph when I'm going 50mph.And gas gauge doesn't work..

 

Someone may have put lower gears in the rearend and not changed the drive/driven speedo gears in the trans to compensate. Or someone may have changed the speedo gears (wrong ones) in the trans for whatever reason. Your gas gauge is an unrelated issue. Either a bad gauge, sending unit, or related wiring.

 

Thanks for your help I will begin my new trouble shooting....BTW alls well on the negitve grounding issue,dual fans are running well,took the car out for a local cruise drove about 60 miles in town.I live in Scottsdale it was 82 degrees and temp gauge stayed between 195/205..I did notice though when fans kicked on when I was at at stop light the cars idle slowed down a bit..

 

Do you need instructions to help with testing fuel gauge?

 

Yes please! Thanks

 

performing the test then the problem is from the trunk to the gauge...

 

Fuel gauge diagnosis