There were three ways the electronic tach was connected over the years:
1. A continuous white wire from ignition switch to coil wrapped around an
inductive pickup on the back of the tach.
2. A white from the ignition switch going into the tach and another one
coming out going to the coil, both via connectors (the pickup is inside the
case).
3. A single white black from coil to tach.
The 73 should have the latter of the three.
PaulH.
----- Original Message -----
From: Evangelos G. Makris <xirias@hol.gr>
To: <mgs@autox.team.net>
Sent: Wednesday, September 27, 2000 7:48 AM
Subject: misleading tachometer
> Hello everyone,
>
> I have checked the tachometer in my 73 B GT (RVC2415/00) against my
> digital car multimeter and a brand new instrument from another maker and
> my suspicions were right:
> a. it shows about 500 rpm more at idle (engine turns at 750, tacho shows
> 1,300)
> b. it won't register more than 3,700 - 4,000.
>
> Having examined the electrical diagrams in my Haynes I've noticed that
> some cars have a "loop" on their tachos, not part of the diagram for my
> car though. Then again there are some errors in those diagrams (e.g. the
> distributor is numbered/called a "lighting switch" in the 73/74 diagrams
> on page 194 and there is no entry for switch #36 in the key on page
> 193). Should my car have such a loop (it doesn't now) and could this be
> the cause of the problem or am I to look for a replacement tacho?
>
> All connections are OK because the other two tachos worked fine.
>
> Cheers
> Evangelos
> 73 BGT
>
>
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