An ignition relay was fitted to late model B's to limit the current through
and hence volt-drop in the ignition switch and wiring although the white
still fed things like the ignition warning light, fuel pump and
overdrive/TCSA. My 1989-published Haynes shows it for both later UK and
North American models. It is the presence of this ignition relay that
causes the non-Dieseling type of running on when the alternator is changed
from stock. I have some extracts from the Workshop Manual and Haynes
covering circuits like turn signals, hazards, charging, starter, wipers as
well as ignition for various years, select 'Spanners', 'Electrics' and
'Schematics'.
The white only went via the tach (for rpm sensing) to the coil from 64 to 72
approx, thereafter the tach was triggered by a white/black from the points
side of the coil. Both types of electronic tach also had a green (fused
ignition).
There has been a starter relay in Bs since 1969/70, and a cooling fan relay
in factory V8s.
PaulH.
----- Original Message -----
From: Skye Poier <skye@ffwd.com>
To: Steve Murphy <k8vo@flyingbeers.org>
Cc: MG Nuts <mgs@autox.team.net>
Sent: Tuesday, December 21, 1999 10:37 PM
Subject: Re: Ignition warning lamp solved!
> Word on the street is that Steve Murphy said:
> > Well, I found the reason for my glowing warning lamp. My car is
> > different from the Haynes diagram which should apply to it, or I'm
looking
> > at the wrong one, or something. According to what I've seen, the ign
> > switched accessories should be fed through the fuse box via the white
wires.
>
> Not exactly, ignition switched circuits are fed by white wires, but
> ignition switched AND fused circuits should be fed by green wires. Err,
> this may be what you just said, but it could be read a few ways.
>
> So, there should be brown going to the ign switch, white off the ign
switch
> going to (a) ignition system coil, tach, etc and (b) the fuse block where
> it turns into green to feed things like the heater fan, wipers and turn
> signals.
>
> Although who knows, maybe the 77 is different. Sounds like you have the
> problem figured out, at any rate.
>
> > Now I'm wondering if there is an appropriate schematic of the wiring
for
> > my car (77B) in perhaps a later Haynes manual? Mine is c1977, and none
of
> > the diagrammes show such a relay... they all show the wiring going to
the
> > fuse block directly from the ignition switch.
>
> I'm not aware of any relays in the B's electrics, it may have been added
> by someone. But again, I'm no expert with the later electrical system.
>
> Good luck!
>
> Skye
>
> --
> 1966 MGB - GHN3L Safety Fast! __,__\__
> The MGB Experience http://www.mgb.bc.ca/ (_o____o_)
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