[Mgs] heater motor wiring

[Barney Gaylord]

Does "all cars" mean all then current year (1972) models of MGB, or 
all prior buiilt MGB as replacement parts?

Even if it is all prior MGB, change of replacement part heater motor 
to "all cars" for MGB in 1972 does not necessarily revert to MGA, 
which is where this thread started.  Concours concious MGA folks may 
not like that idea.  The polarity sensitive MGB motor can be 
connected to turn the right way for MGA, but is it equal or better 
than the original part?  I have seen a heater motor for the MGB-V8, 
had one in my hands once and sent it back.  The thing is at least one 
inch shorter than the earlier motors, and all of that length is taken 
away from length of armature coils and field magnets.  Can a motor 
half as long internally be as powerful?

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?


At 09:00 AM 1/5/2011 +0000, Paul Hunt wrote:
>FWIW the '2 speed' heater fan consists of a single-speed motor with 
>a dropper resistor inside the heater unit casing.  For the first 
>speed the current goes via the resistor to the motor, for the second 
>speed the resistor is bypassed.  The resistor is in the air flow for 
>cooling (common in more modern cars).
>
>The Parts Catalogue indicates the motor was changed for *all* cars 
>when the V8 was introduced in Dec 72, certainly by that time they 
>are polarity sensitive.
>....


>----- Original Message -----
>>...  MGB 1975-1980 heater motor has three wires (possibly two speed?).