So on my bf's 96 12v the odometer, speedometer and tachometer all quit. All the other gauges on the instrument panel works. About a week ago the speedo and tach started dancing around and the generator and check engine light would flash while the gauges were going crazy. What would cause just those three things to go out?

 

it needs a cluster or it might be a bad ground

 

If your truck has a speedo sensor on the rear end of the tranny,it may be whats causing the speedo issue.

 

sounds like either a circuit ground or an unhappy instrument cluster. Might have to check the connections on the back of it.

The rear VSS could affect the speedo n odometer but the tach n rest of cluster should still work fine......those issues kinda sound like either a connection or possibly a computer on the fritz....check connections n grounds first.

 

I would have guessed the speed sensor too but the fact that the tach went out also sounds like the cluster needs replacing. Or by coincidence your ckp sensor, and vss went out at the same time