Very interesing...
I have an 85 non CA car, and the tach does not work on it...
I looked under the hood for the amplifier, thinking I could just take the one from my car and use it... simple repair, right??!?
Well, my 85 has a low-profile cap on the ports where the tall garbage can looking amp would normally sit, like it did on my 85. The holes for the old faashioned type of amp are still there under the cap. Yet, I don't recall if there is even any wires coming or going from it.
Phil's site shows an item for my car (VIN after -A-007353) as an inductive lead from a bellhousing. It looks like this:
the old one looks like this:
The question becomes how does one start troubleshooting the later, newer style of tachometer leads... and does the instrument cluster input change as compared to the older style ones... as if it does, and I find it to be a circuit board or cluster issue, then I can't use my old one from my 83 as a swap-in...
Thanks!
JMH