I have a 1983 Nissan 280ZX coupe, automatic with digital speedometer. The speedometer does not register correctly and bounces up and down. I don”t know if the speedometer was changed before I bought the car. The speedometer cable is hooked directly to the speedometer. I have gotten some information, on line, that there is supposed to be a pulse generator by the battery which the cable is supposed to hook up to. I can”t find anything that might look like this around the battery, don”t really know what it is supposed to look like. Nothing with wires going to the dash. Also it does not have a digital climate control. I need to find out if the speedometer has been changed, so that I can get it fixed properly. I live close to Las Vegas, so can go there if anybody knows a reliable repair person.
On the early speedo the cable hooked directly to the speedometer head the pulse generator is built in . I think you need a new speedometer head and cable. this is a rare set up it could be hard to find parts.