Fuel gauge question?

[chinacat]

Hey All,

Need tome expert Thing knowledge here: my fuel gauge is not giving me accurate readings (i.e., when I fill the tank, it stays wherever it was prior to filling; it has a tendency to move up and down about two quarters in either direction every now and then, etc.) I'm pretty sure it's not the sending unit in the tank, because when I tap on the speedometer enough with my knuckles, the gauge usually moves up to a more or less accurate reading (then promptly goes back down again when I stop tapping). Any ideas here? I read something somewhere about a vibration unit for the fuel gauge, but I've never taken one apart/fixed one before. Any advice is greatly appreciated.

[Marc]

On the backside of the speedo near the top there's a small rectangular box - that's the "vibrator" or voltage regulator for the gas gauge. It has a power wire feeding it on the passenger side and its output lug is secured to one of the terminals on the gauge. Check all of the connections for tightness - the two brass nuts on the gauge in particular - and probe the vibrator output with a testlight. With the key on the light should pulse steadily - if it's erratic or there's a several second delay between pulses replace it (any `68-up Type I part will do). Note that the small screw which mounts it to the speedo MUST be tight - that's the path to ground for excess voltage, turning the key on without the vibrator grounded can burn out the gauge.

[chinacat]

Thanks Marc, this is some very helpful info!