Help! '81 tachometer

[ladams]

I just tried to start my '81 and found the battery to be dead. But, as it died and the engine was turning over, my tach shot up to max and is stuck there. I charged the battery and started the car up but still no luck.
Any ideas?

 

[bill81vette]

I'd be willing to bet that the printed circuit board that operates it went bye-bye..
time for a new one!!

 

[6880 Mike]

Unplug it at the distributor and see if it drops back to zero.

 

[pbcanney]

Unplug it at the distributor and see if it drops back to zero.

what he said....

maybe you'll be lucky and just 'lost' the filter between the distributor and gauge

 

[RC81]

Mine has done that a couple times and comes back down after I drive it a bit. Seems to happen only when the battery runs down.

 

[ladams]

strangest thing...

I was itching to get the car out of the garage to wash off the winter dust today, so I started her up and let her warm a bit. I put it in gear and holy cow!!! The engine revved so high that I almost backed into the wall, then all of a sudden I put it in park and at the same time the tach started working again. What the heck!?!?!