93 speedo sits at 140 miles per hour

[jeffbolin]

I have a 93 transport that when you put the key into the ignition and start it you can see the speedo power to the full scale indication from aboput the 110 mph reading. this started when I was trying to jump start the car and the battery was bad so the charger was surging trying to provide the current but then seeing the bad battery and shutting down and back and fourth this happened for about a minute then the speedo pegged and won't go back to zero key on key off no matter still pegged but doesnt appear to b e mechanically stuck
any one have any ideas?