Russ P

The tack on my 86 Carrera started to 'fly away', as in it would read way high, floating towards the peg beyond redline. I connected a test lead to the battery posts, and read the DVM when idling, when driving, etc, and saw that the voltage dipped to about 12.2 v when the tach would 'fly away'.
Previous advice said that it was most likely a voltage regualtor, as this had happened to a few listers. I had a new alternator and voltage regulator, and thought the problem was solved. Last time I drove it, I had the lights and the stereo on, and the tach starting going nuts again! I noticed that after turning on the heater fan, it went even further, so it seemed the more current I was drawing the worse the problem. With the lights and the heat off, it works fine.
I heard about some kind of control chip under the passenger seat, but found no information in the Haynes manual.
Can someone provide me with the resolution to this problem?
Thanks in advance,

Russ Pesko
Chicago PCA
Rennlist 020228-3507

Huey58

Hello Russ!

Had the same problem on my 86' cab. It ended up being the ground strap underneath the car. It had rusted just enough to alter the current in the car. Had the dealer replace the strap, bouncy tach
and light problems went away!