My Speedo, Temperature and Fuel gauges all stick sometimes; and a whack fixes them all for the rest of the trip. I don't think it's bad soldering because the one whack keeps them going for the rest of the trip and usually for a few days for the small gauges and a few months for the speedo. I think it's just sticky old lubrication. Dry joints (bad soldering) is usually much more intermittent, like my 85 Bluebird with vacuum fluorescent gauges. It's like a disco in that car sometimes!