Thanks again to all who responded
Pete
85 STI
Seattle
Tamara Saarinen wrote:
>
> Martin Karo replied to Peter Young:
>
> I think on your car the tach pickups are on top of the coil. Have you
> checked them? If any are missing or detached, voila. If not,
> nevertheless, cleaning the spade connectors and outright replacing the
> female connectors might solve your problem.
>
> >>> Peter Young <pyou@u.washington.edu> 03/09 1:44 AM >>>
> I've got a non functioning Tachometer on an '85 505 STI. I've never seen
> it work and am trying to work from a haynes manual which doesn't offer
> much info on it (as far as I can tell). Looking at the wiring diagrams I
> get the impression that the 'Rev counter' is fed by a wire coming from
> the tachymetric relay which I think I finally found under the steering
> wheel. The question is, can this be tested or fixed or should I just
> replace it? Is this even the problem or is it further along in the
> spider web of wires. The guy I bought the car from claims it gave up the
> ghost one day and he couldn't determine whether it was the sender or
> not. He couldn't even find the sender unit which is understandable since
> he was working from the very same Haynes manual. Is there a sender unit?
> It seems to me that the tach would be fed from the ignition circuit
> somehow. If anybody has any ideas, they would be much appreciated.
>
> Pete,
>
> Busy last night, but here is our tuppence:
>
> We support Martin. Wire 112 (probably) takes the signal off the coil for
> use by the fuel injection system and by the tach. Via wire 112A, it goes to
> the fuel pump tachy relay, then branches off that pin as wire 112 to the
> tachometer. So cleaning the pin on the tachy relay won't help a
> nonfunctioning tach, but your fuel pump will be pleased! AND, if your fuel
> pump is working OK there isn't anything wrong with the signal from the
> coil. You could have a break in the wire 112 somewhere from where it
> connects to 112A on the tachy relay to its connection on the tach.
>
> ALSO, there is another wire supplying a signal to the tach: The wire is 32B
> (again, probably), and the signal is power from fuse 8, the same fuse that
> supplies power to components in the fuel control system. Again, with the
> fuel system working OK, the problem is not the power level from the fuse to
> the place where wire 32B branches off to the tach, but could be that power
> is lost somewhere from there to the tach along 32B.
>
> ALSO, there is a wire M (it says here) which goes from the tach to ground
> at the G4 connection located near the lefthand headlight (inside the frame
> just to the left of the radiator). This ground actually is reached by a
> path from the tach on the instrument board to the ground connection on the
> instrument board, THEN along wire M to the fuse block, then along M again
> from the fuse block to G4! Could there be a break between the tach and the
> fuse block. Yup. If not, there seems to be no other indication for bad
> wiring, and the tach becomes suspect.
>
> Isn't wiring fun!?! At this point, you may wish to forget the tach ... or
> get a model T.
>
> Keep us posted on your tach travails.
>
> Gene & Tamara