Hi all, new to forum, not to Ford. I've been a FMC tech for 20yrs. I find myself driving a 1997 F150 4.6l auto, had 112,000 on the odometer when it quit.
I'll confess, I've replaced many instrument clusters for this concern, (the life of a dealership flat rate tech) however, I'd like to know if anyone has repaired one. This one is my daily driver and I would like to save a buck or two if possible. BTW, the speedometer works.
Pull the cluster,and visually track down the runs that go from the connector to the Tach connector.
Use a meter,and check for continuity between the main connector,and both tach terminals. if either is open, youve found the problem.Usually it will just be corrosion.
If continuity is good,check across the tach terminals.You should read a low resistance.....Id guess around 10-40 ohms.If this checks good,I figure the cluster itself is good,and the problem would be in the engine compartment where the tach feed comes from.
Hope this helps. I do suggest a Digital DVM such as a Fluke 75/7700 series.
I have the same problem with my 97. stopped at 70,999. I was going to try to pull the cluster and spin it by hand to get it working again. title already says odometer discrepancy so I am just doing it for oil changes and such.