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Re: Heater motor

To: <mgs@autox.team.net>, "Barney Gaylord" <barneymg@ntsource.com>
Subject: Re: Heater motor
From: paul.hunt1@virgin.net
Date: Fri, 21 Jul 2000 10:59:10 +0100
----- Original Message -----
From: Barney Gaylord <barneymg@ntsource.com>
To: <paul.hunt1@virgin.net>; <mgs@autox.team.net>
Sent: Thursday, July 20, 2000 10:02 PM
Subject: Re: Heater motor


> At 07:10 PM 7/20/2000 +0100, paul.hunt1@virgin.net wrote:
> > the heater motors on both my MGBs exhibit significantly different output
> volumes according to which way the supply and ground are connected to the
> motor.
>
> The possibility of bad connections aside, do you know if this actually
> reverses the direction of the motor?

Definitely.

> >.... when I got my V8 as a daily driver I noticed the heater output was
> significantly less than that of my roadster. .... I took both motors out
> and found them identical but that they rotated in different directions.
> Reversing the connections on the V8 brought it up to the same
'performance'.
>
> Does this mean that the direction reversed, or only that it ran faster?

See above.  Does yours run at different speeds with different polarities,
albeit in the same direction?

> >Can't speak for how the MGA is wound or how it differs from the MGB, have
> you tried reversing yours just to see what happens, ....
>
> Yup, many times, and I did that again just before my recent posting just
to
> be sure.  The MGA heater motor always runs the same direction and speed
> regardless of polarity.  Furthermore, every MGA heater motor I have seen
> (quite a few) has two black wires, so there's no way to tell which is
which
> without opening the motor case.  Do the later MGB motors have color coded
> wires?

Yes, green/yellow and black on both the motor and the harness on my 73 and
75.

> V.B. lists one part number for the heater motor for all MGA and MGB,
> including the twin cam (opposite rotational direction) and V8 (shorter
> motor case).  Big laugh.  I bought one of these motors from V.B. a couple
> of years ago and promptly returned it.  That motor has the same cross
> section as my original motor but is a full one inch shorter in the field
> coils and armature and outside case.  I have been told that this was done
> to accomodate a space restriction with the introduction of the V8 in the
> BGT.  I suspect this motor will not have the same power or blowing
capacity
> as the larger units.  I never powered it up to see which way it runs, and
> neither did I notice if it may have had color coded wire leads.

An old UK Moss catalogue also lists only one part number but the current US
Moss lists two with the change-over point being the start of MkII production
which was also when the polarity changed.

> So here is the next reasonable guess.  Perhaps the newer replacement
motors
> are wound differently and designed to change rotation with polarity.  This
> would solve a sales volume and stocking problem by replacing multiple part
> numbers with one common part.  I notice that Moss does not have a part
> number for the MGA heater motor, but does have two different numbers for
> the MGB motors.  Oh Kelvin, are you there?
>
> Barney Gaylord
> 1958 MGA with an attitude
>     http://www.ntsource.com/~barneymg
>
>


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