Well if it was my car here is what I would do. I would start off going here Wiring Diagrams 308 365 400i 512 and get an electronic copy of your wiring diagram. Your profile isn't filled out so not sure what car you have but they have diagrams for the 365 GT4 and 400i. I would then trace the wire on the diagram to see where it goes and then look for the wire in the car and see if I could visually see any thing like a loose or broken wire. If I didn't see any thing obvious I would take the instrument panel out and then look at the wires hooked up to the tach. I'd then take my dwell meter which also has a tach function and connect it to the wires on the tach in the car and then start the car. If my dwell meter showed an RPM reading then I would ascertain the tach was bad. If the dwell meter didn't show an rpm reading I would further investigate to wiring in the car. Definitely not an easy job but not impossible.
You could remove the instrument panel - not too tricky - to access the tachometer and disconnect it. Then rev the engine and see if the jobby is turning - I'm assuming it is mechanical!
Interesting, must have changed for 1975. POS computer. I have tried posting this picture multiple times. I rotated and saved the picture in all orientations and it is still upside down. Image Unavailable, Please Login
Thank you Ak Jim and aidanparte for your constructive inputs. Wishing you all a very Happy Thanksgiving!
Southern hemisphere car? The only hack I have for a iPhone is to copy the picture onto a word document right side up and then save the image from there. Then the image seems to attach correctly. Beats standing on my head to look at the picture!
