so i started my car today, and noticed that as the car started the speedometer jumped up to 100 mph, and then fell. this happened every time that i started my car throughout the day. then on the drive home, the temp meter was jumping up and down like nuts, at the same time, the radio was acting a little crazy. Any ideas?

 

maybe alternator. Check your voltage. Should be 12.5-14.5 Volts.

 

Need more info! What year is your car? mani tranny or auto tranny? have you done any electrical upgrades lately?