Originally Posted by
Cooter
The neutral light in my Ss would do that. It was dirty, but they are so cheap I would just replace it. Make sure it seats well (needs a good ground) and the terminal has a good connection.
Since the gauge cluster only has one power source wire to power both the tach and speedo/odo, means the break is internal (inside the cluster). Replace it with one of the same mileage or take it apart and have a look-see at the inside. If you are handy, it is a easy job and hard to screw anything up.