sounds like the alternator id have it cheeked at auto zone for free
An auto battery could be leaking for a couple of reasons. The alternator could be overcharging the battery causing the leakage. Or the battery itself could have a short or other internal problem causing it to leak when charging.
Dead cell in the battery itself which requires you replace the battery. Can also be any light on the vehicle that is on pulling power from the battery. It can also be a relay that is stuck closed.
The key being in the "on" position itself. As for rapid battery drain, you could have a bad battery or there could be a loose connector. Source: Personal experience
Most likely a faulty regulator causing a over charge
If speedometer itself is working then gears inside the assembly are damaged.
Either the Speedometer itself is bad or the speedometer cable is. either one isn't too difficult if you have pulled a dashboard out before.
If it's old enough to have a mechanical speedometer, it'll be in the speedometer itself. If it has an electronic speedometer, there is no speedometer gear - to recalibrate the speedometer to match something like, say, changing tire size would require changing the parameters in the engine ECM.
Start with the battery terminals and connections on the other ends of the battery wires. Check the battery itself as a loose plate in the battery could be heating up and shorting the battery for a moment causing the problem.
You need to determine if it's the speedometer itself that's faulty, or the vehicle speed sensor. If the speedometer is faulty, you'll need to replace the instrument cluster.
I had that same problem and I had to replace my dash cluster.
You would fix it by replacing the instrument cluster. The speedometer itself may not be faulty, it is more likely to be a problem with the speed sensor.
There is a Vehicle speed sensor on your vehicle. There is no cable running to your speedometer so I would start with that sensor.... Correct answer: The sensor is usually fine. The speedometer itself goes bad. They sell on ebay, used, for $80 or less. Buy the whole cluster, and swap the speedometer into your cluster. Make sure the seller describes if the cluster is from a 4 cylinder car, or a 6 cyl, they don't interchange. ABS or not, doesn't matter, just swap the speedo in to your own cluster.