By 'all cars' I mean both 4-cylinder and V8, from that point on.
As I said before the motor itself still only had two wires i.e. was
single-speed even for the 2-speed system, the lower speed being obtained by
passing the current through a dropper resistor in series with the motor as
is common in many other cars, especially with 3-, 4- and 5-speed fans. The
motor part number *did* change when the 2-speed system was introduced,
whether that was a more powerful motor to make better use of the two speeds
('half' the speed of the original motor wouldn't be much use to anyone,
being a bit like the panel light dimmer ...) or for other reasons I don't
know. The motor for the 2-speed system doesn't seem to project any more
from the back of the heater casing in photographs than the previous one, I
haven't measured them but I could. Don't forget the motor body projects
inside the casing as well as outside, there could have been a rearrangement
there i.e. simply moving the mounting flange back to put more of the motor
inside the heater casing in 1972.
I'm not aware of a 3-speed motor being provided on the MGB, unless you
include 'off'.
Incidentally the two motor wires may have been black originally, that is
what Clausager appears to show for a 62, but for a 64 and a 69 they are
clearly both white which implies the polarity insensitive motor was still
being used at that point. 72 and later models have the different-coloured
motor wires.
PaulH.
----- Original Message -----
> Does "all cars" mean all then current year (1972) models of MGB, or all
> prior buiilt MGB as replacement parts?
>
> What's the heater motor look like after the change for '75 North American
> and '77 UK models when they changed to three wires? I suppose that was
> after the V8 was out of production, and the shorter motor was no longer
> required. Three speed without a resistor, Maybe?
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