If the power supply to the tach electronics (green and black) that could
well have damaged the transistors, there is a schematic at
http://www.classictiger.com/techtips/motach.html but check you do have 12v
at the green and black first.
The voltage stabiliser is nothing to do with the tach (except that they
share a common 12v supply from the green), the stabiliser only feeds the
fuel gauge, electric temp gauge, and electric oil gauge on some years.
On a four-fuse fusebox the two top fuses feed the parking lights (and
side-marker lights 72-on), one fuse per side. The two terminals on the
front are connected internally, so there should only be a single red/green
on *one* of them, which one doesn't matter. There should be two reds on
each of the two terminals on the back of the fusebox. Not DPO, factory.
----- Original Message -----
From: "Tim Baxter" <baxter@gretschpages.com>
To: <mgs@autox.team.net>
Sent: Wednesday, October 23, 2002 6:37 PM
Subject: Tachometer
> Hey all... I need tachometer help. Car is a 70 GT.
> All guages are working except tach and speedo. Speedo appears to be a
> shot drive cable.
> The tach/coil circuit appears to be intact, and if I pull a white wire
> from the tach with the engine running, the car dies. Consulting the
> schematic (#9 or 10 in Bentley, haven't quite sorted that out yet,
> since I appear to be on the cusp)
> it appears all wiring to the tach is in place and good. Two white
> wires, one with a female and one with a male end. Two green wires
> going into a common female end. Ground wires are on securely (don't
> know where they are on the other end.)
> When I got the car, the tach was hooked up backwards, I believe, which
> is why it wouldn't run. Could that have fried the tach?
> I'm also pondering the voltage stabilizer dealey, but I think it would
> probably affect other instruments, too.
> SO whaddaya think? Any way to test a tach? What should I look at next.
>
> On a side note, anyone know offhand what belongs to the second fuse
> from the top on a 70?
> Apparently I have NOTHING hooked to that fuse. DPOs.
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