For the MGB as well as the the coiled wire (and that is only on the earlier
electronic tachs) the internal supply connections to the electronics must be
reversed as well, as John Twist in the Moss cataloge says. Even tachs with
the loop have three different ways of connecting the white wires, and for
tachs with the internal loop and male and female connectors on the case of
the tach you will have to reverse the internal loop, or swap over the
connectors on the wires, or find the bullets further down the white wires
and reverse those.
The wiper motor will run backwards. You may not notice, but on the other
hand you could find the blades stopping in a slightly different position,
but is easily dealt with by altering the position of the arms on the
splines.
I disagree with Moss when they say that heater blower motors do not need to
be changed. The efficiency of the fan various enormously with direction of
rotation, and since the motor has a permament magnet 'stator', just like the
wiper motor, it will rotate backwards if you reverse the battery
connections. Anyone can see the effect of this by reversing the connections
at the bullet connectors at the motor, and this is one of the first things I
recommend is checked where people complain about poor heater output.
In my opinion Moss glosses over it a bit, but as far as battery connections
go both my cars have different-sized positive and negative clamps, so the
clamps on the cables have to be changed before the cables can be connected
the other way round.
PaulH.
----- Original Message -----
From: Brian Warmuth <warmuthb@WLSC.WVNET.EDU>
To: Maffei Andrew P SSgt 27 LG/LGQPT <Andrew.Maffei@cannon.af.mil>;
<mgs@autox.team.net>
Sent: Friday, June 23, 2000 2:49 PM
Subject: Re: Pos to neg
> Well, I don't have that problem because my tach is mechanical drive.
> Yours is electric and requires you to take it out of the instrument
> panel , I believe take the tach rear cover off and "reverse" the coiled
> wire located inside. At one time there were detailed instructions on how
> to do this in a Moss Motors catalog or magazine. Perhaps someone can
> help you with that. I don't know the exact process.
>
> Brian Warmuth
>
> Maffei Andrew P SSgt 27 LG/LGQPT wrote:
> >
> > Someone did that to my 66B, I think it was when they swapped the
generator
> > to an alternator. now I don't really know how it's done, but the only
> > problem now is the original tach will not work at all, and I have tried.
> > if anyone out there knows how to fix this please let me know ( and yes I
did
> > try swapping the wires at the coil)
> >
> > > -----Original Message-----
> > > From: Brian Warmuth [SMTP:warmuthb@WLSC.WVNET.EDU]
> > > Sent: Friday, June 23, 2000 6:28 AM
> > > To: mgs@autox.team.net
> > > Subject: Pos to neg
> > >
> > > I suppose this topic has been covered before and there are probably
some
> > > web-pages which deal with the specifics of the process, but I would
like
> > > to convert my MGA from the positive ground to negative ground
> > > arrangement. I believe it is fairly easily done, but does anybody
have
> > > a step-by-step? It has the original fuel pump, however I have a
rebuilt
> > > one (converted to operate on negative ground) to install. Since the
car
> > > has no "electrical" gauge do you just switch the battery ground,
switch
> > > the coil wires, and re-polarize the generator?
> > >
> > > Mucho TIA!
> > > Brian Warmuth
> > > 52 TD (Rhd), 58 ZB, 59 MGA (1500), 60 Farina Magnette
>
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