you have either a bad speed sensor (check engine light on?) or a short in the printed panel and amp/ voltage reg. on the back of the speedo head. no check engine light on replace/ rebuild speedo head there are speedo shops. if light is on replace speed sensor as the OBD system uses this sensor to. clear codes and happy driving Johnie
why is a nonelectronic speedometer needle bouncing
Stop driving it
A 1991 dodge dynasty speedometer bouncing could be a sticking speedometer cable, or a bad drive gear. Check the cable first, and lubricate it to see if the problem stops.
Try disconecting the speedometer cable and squirt some lube in it. It might have dried out.
Try asking your question again - it makes no sense as presently written. If the vehicle won't start - then it won't run. If it won't run how can the speedometer needle be bouncing? (?????)
Possibly your speed sensor. My speedometer would bounce around & then soon after it felt like my transmission was slipping. Turns out the speed sensor controls the upshift in your transmission.
Replace the speed sensor, usually mounted on the transmission bellhousing.
If the speedometer needle is going crazy and not working properly, it is probably the speedometer mechanism that needs to be replaced. It could also mean the vehicle is having a transmission slippage problem if the needle is bouncing back and forth.
A bouncing speedometer needle could be caused by a loose or damaged speed sensor cable, a faulty speed sensor or a problem with the instrument cluster. It is best to have a mechanic diagnose and repair the issue.
Unhook the speedometer cable from the transmission and the instrument cluster in the dash. Take the actually metal cable out. Clean it with solvent. Re-grease with "lithium-based" lubricant. Re-insert. Also check for fraying. If so, replace cable.
I had the same issue with my 93 ford tempo, it turned out to be a governer gear in the tansmission that would cause it to spike the speedometer. If you get it looked at quick you will save lots of cash.
Fixing it depends on what the speedometer is doing. Chances are its making a funny noise and the needle is bouncing around. This would be due to a damaged or unlubricated speedometer cable. It is a cable that spins around in a plastic sheath connected to the back or your speedometer and to your transmission. Often times removing it and filling it with graphite powder will solve the problem. If its severely damaged you can replace it with a new one. If the cable isn't the problem you may have to replace the speedometer itself.