Most of the time the Tach works normally but it intermittently drops back to zero for a while then starts working. The speedometer works normally all the time. I am trouble shooting with Ford factory manuals volume 1, volume 2, and wiring diagrams. I do not know what the symbol on page 413-01-25 means (see attached pic). What are the 4 positions?
Any help would be greatly appreciated.

 

Key position? test is calling for power on it looks like, maybe even running? I have never seen that symbology before.

 

Thanks for getting back. This was my thought also. I tried to add another page from the manual that describes a test for "ground" that indicated position "0" or off which makes sense however I was not able to upload it in this reply? I will disconnect the harness & see what I find.

 

You might check the front of the wiring manual for this but I believe it is a setting on the Ford Scan Tool when it is connected to the socket under the steering column.

 

still having this problem any Ideas? I have the instrument cluster out now any help would be greatly appreciated

 

I have ford shop manuals including wiring diagrams

 

You should have 3 connectors on the back of the cluster

C220A
C220B
C220C

C220A pin15 should be Tan/yellow stripe wire, it runs to Pin48 on the Computer(PCM), Power train control module
This is the actual RPM signal from the engine

But there is also a separate Ground for the Tach
C220C pin8 a Black/yellow stripe wire, if it is loose then tach will lose RPMs

Power for the Tach comes from C220A pin13, but if it was loose then other instruments would be effected

Could even be a loose connection in the instrument cluster