Join Date: Dec 2001
Location: Belleville, Illinois
Thanked 22 Times in 17 Posts
Re: Odometer works, speedometer doesn\'t - how to f
The speedo is extremely simple. There's a magnet attached to the end of the cable. It spins inside a copper cup attached to the indicator needle. As the magnet spins it places a very small drag on the cup that's counteracted by a weak spring. The faster the magnet spins the more drag is applied to the cup and the farther the needle moves.
If the needle pegs almost as soon as you start moving, the spring is broken.
If the needle bounces rythmically the cable has a kink.
If the needle doesn't move at all or very slowly the lubricant has probably gotten gummed up. You can take the instrument apart by prying the chrome ring away from the housing with a small screwdriver.
Alcohol would probably be the best cleaning solvent. Unfortunately I don't know what to lube the mechanism with, but my guess would be powdered graphite if anything. If there is no speedometer shop near you perhaps a clock repairman could offer some advice.