'95 Pathfinder Tachometer problems

I went to Spaulding Wrecking in Spokane today.

Asked the clerk about the Speedometer dash unit and he said Pathfinders always had a problem with the Tachometers.

He told me that the usual problem is normally in the Fusible Links on the Positive (+) battery post connector - bad connections.

So I looked at mine out in their parking lot.
I took the links out of the Battery side of the cable connector and re-inserted them.
http://alkaspace.com/usr/3754/Fusable_Links.J.jpg

The Tach then worked on the way home - EXCEPT - when I took the transmission out of overdrive (button out),
the Tach went crazy - needle flipped back and forth like crazy !
Then returned to working fine - with the overdrive button in.

I will scrape the contacts and coat them with Zinc Oxide Ointment.
That is an electronics repair trick I learned from my DAD who worked at an electronics plant
as the Head of R&D (Hallicrafter's Radio) in the 1950's and 60's.

I have no idea what is going on with the Overdrive selector button....

I suspect that the Tachometer itself is fine - just screwy connections somewhere in the
wiring - which must be very complicated.

I cannot find the Tach in the wiring diagrams in the Chilton Manual !

Has anyone had this problem with their Tachometer going bonzo ?
Was it fixable ?

DoctorBill