Third gen IROC RPM gauge stuck

[86 IROC-Z]

The RPM gauge on my 1986 IROC is stuck at the red line. I've been having problems with my alternator (actually fixed it just this morning) and have had a dead battery on start up a few times because of it. The problem is fixed now, but the other morning while trying to start the engine, it was cranking but not firing (not enough juice in the battery) but while I was cranking it the RPM gauge went up and around, and pinned itself at the redline (7000 RPM, 3o'clock position).

If I tap the plastic covering, the needle start going back up to lower RPMs, but when I start the engine the gauge shoots back and pins itself again, while the engines RPM are completely normal. Does anyone know what happened? I can only guess that maybe a sensor blew while I was cranking... any suggestions?

[ss~zoso~ss]

no idea dude, are you a member of a 3rd gen forum, that might be your best bet

[AKIRA]

Man oh man I remember having tach problems with my 89 formula. My tach had a life of its own. Do you have MSD ignition by chance?

[86 IROC-Z]

Man oh man I remember having tach problems with my 89 formula. My tach had a life of its own. Do you have MSD ignition by chance?

Nope, everythings stock...

no idea dude, are you a member of a 3rd gen forum, that might be your best bet

Yeah, I just figured I'd check here before hand, just in case.