Speedo Misbehavior - 1984 Eldo FWD
 

My speedo indicator needle does not rise off zero until car reaches about 35 or 40 mph. Thereafter the indicator is steady. Also seems to read a little low but haven't compared its readings against another tag-along vehicle. The cruise control works okay but haven't used it at low speeds.

The tranny is currently over-filled but that will be fixed next week. A friend mechanic thought that might affect the speedo.

So I guess no one knows anything about speedometers. Cadillac manual has no trouble-shooting section offering advice.

Had tranny fixed. Did/Does not affect speedo problem.

Have you tried to lube the cable?

slowroll .... yes, cleaned and relubed cable. This is a mechanical speedo and does have a drive cable; the car has been sitting in garages all its life (only 51,000 m on it).

When starting from a stop, the dash gauge stays on "0" until I get above about 35 mph and then it shows speeds above that level. Odometer registers mileage at all times which indicates the dash unit is getting the info. I can't confirm the speed shown or mileage displayed is accurate but both seem reasonable.

By deduction: When the indicator needle is showing a reading, the needle is steady. That seems to say the cable gear head at the tranny connection must be turning smoothly - apparently isn't missing any teeth.

Thus .... (1) like many older cars, the indicator needle is probably mounted on a rotating magnetic cup-like device and perhaps lost its magnetic strength ? .... and/or .... (2) is the bearing that supports the indicator cup binding ?

Unless you have other thoughts, guess I kind of answered my own question. Finding a working junkie unit near impossible and sending unit out to instrument rebuilder = more than $200. Maybe drive it as-is.

Thanks for your consideration.