Report Avanti II Tach in 1965-83 Avanti Posted November 20, 2015 · Edited November 20, 2015 by WayneC Any suggestions for sources or fixes? Today I was looking through a stash of Microsoft Word documents I've saved over the years, some of which are Avanti-related, and I came across this (perhaps it'll be of some help) I'm not sure whether I wrote it, or if I found it somewhere... Thoughts on checking a bad tachometer on an Avanti: Luckily I haven`t had to worry about this problem as yet, but here`s a couple of hints and thoughts: start by checking all the wiring to the tach sender and the tach itself for loose or corroded connections. The tach sender is a flat cannister about 4 inches in diameter by a half inch high, located on top of the horizontal steel dash support, just below and to the right of the tach head. There are 4 terminals on top of it. The tach sender gets its rpm timing signal from the negative terminal on the coil to the terminal marked `D`. The sender gets 12v from the circuit used for the automatic shifter... this is the 2-amp fuse in the fusebox closest to the circuit breakers... check the fuse and check for 12v to the sender terminal marked `+`. There is a terminal marked with the grounding symbol which should have a white ground wire attached... check this wire for continuity to body ground. Lastly, there is a yellow wire from the tach sender terminal marked `M` to the brass terminal on the back of the tach head. On the tach head there also are 2 black power leads for night illumination bulbs, and 2 white leads for ground for those same bulbs. I`m not an electrical techie so I do not know how to check for the signal from the coil to the tach sender `D` terminal and from the sender to the head (yellow wire) but I guess I`d play with the 12v setting on a fuse-protected ohmmeter to see if that picks up any kind of reading at the `D` and `M` terminals on the sender and the brass terminal at the tach head that varies with engine rpm. Hope that all made some sense.