[Peter Serio]

This is most common failure mode which all 1965 and up GM car gauges have. Your pointer falling off all by itself is a sure sign the internal magnet-coil is out of it's original factory fill buffering fluid. It is only 2 or 3 drops of fluid to start with and after many years it leaks out. Here is a photo of wire windings, of that style gauge. The fluid is inside the very center of the nylon former, you cannot see it.

The fluid serves 2 purposes: 1) as lubrication for the moving parts of the gauge, and 2) it slows down the reaction time of the moving pointer by about one second. This is very important as those electro-magnet coils (key on) are wired to full 12 volts battery +. Once the fluid is no longer in there the pointer will move in "real time" that is too much for the micro-tiny shaft and hub; after a while the pointer gets loose on the end of the shaft, the hub then twists on it's shaft (throwing the gauge completely out of calibration) and then, finally the pointer falls off.

Putting it back on using super-glue or loctite is not really a good way to fix that.

After 50 years this always happens, there is nothing you can do to stop it. Since these cars are all over 50 years old now this can be a real problem, typically for the first 10 or 15 years of the car's life, the fluid stays put. But after many more years, if you drive the car or just let it sit, it does not matter. That fluid will find it's way out.


The cure is one or the other. First determine if the nylon former and wire are both still good. And replace the buffering fluid, or 2 replace the whole magnet-coil with a brand new coil. After you do that the gauge must be tested and re-calibrated using it's sender; either way.