Rev Counter problem

[pridaux]

Hi Guys can anyone help here the rev counter is acting up it works for a while ok mainly when car is warming up then it starts jumping and finally goes all the way into the red and stays there
Its a 78 911sc Targa I also cant seem to work out where it is connected on the engine as I wanted to check connections where clean and correct if anyone can post a picture where it is in the engine bay that would be fantastic
Thanks

[sportsandclassic]

Hi, the connection is at the ignition coil. Check the wires to it and figure out which one goes to the rev counter.

Maybe loose or shorted out..?

Mike

[pridaux]

Hi Mike there where only 2 wires to the coil seemed ok but have taken off and cleaned connections and tightened up I guess if it still happens will have to investigate further
Andrew