Bouncing tach and stuck MPG gauge

[tbrewster]

Replaced my alternator with a reman from Autozone and now I'm experiencing some problems with my tach. While driving at a steady speed (~2500 rpms) the tach would up to 3000 rpms+ periodically then back down.

Also, at times the MPG gauge would not work. Sometimes it stays all the way left, all the way right or around 10-15 mpg. It'll stay that way until I shut the engine off and restart the car.

Thinking perhaps i got a bad alternator. Never had an issue with my tach until the alternator replacement.

Thoughts?

Thanks for your inputs...

[Ceeker]

doubt it. Your tach is electronically controlled. Alt just has to do with the voltage and charging system - nothing to do with your tach or gauge underneath. I would swap another cluster in and see if anything changes. If so, then you have a problem with your circuit (SI board batteries) or a shorting tach.

[jlevie]

That would make me think first of a bad SI board in the cluster and second of a bad tach/mpg unit.