[Mgs] Heater Motor

Barney Gaylord barneymg at mgaguru.com
Mon Dec 10 20:37:56 MST 2007


At 09:03 PM 12/10/2007 -0500, Ed Woods wrote:
>....
>Well, the motor's out and partially dismantled: two major pieces. 
>Does the armature simply pull out of its half of the outer case?

Yes.  It should have a plain smooth shaft passing through a 
self-aligning spherical bronze bushings at both ends (blind in the tail end).

>Seems to be great resistance to separation of these two parts. The 
>bearing on the drive end of the armature shaft appears to be 
>binding. I'd like to lube it, then reassemble the whole thing.and 
>give it a try again.

A common malady is a heater motor that squeels loudly when it's 
cold.  A drop of oil on the bronze bushings will often stop the 
noise, at least for a while.  If it has been running dry too long and 
is a little worn the noise may come back again after more running 
time and teh next cold snap.

>When reassembling, how are the brushes fit to the comm? Is the 
>armature assembled to the brush rigging and then inserted into the 
>half of the case containing the field magnets and drive end bearing? 
>Anyone out there done this?

I have pictures of the overhaul and reassembly here:
http://mgaguru.com/mgtech/electric/ht_mtr_1.htm

Note that MGA and early MGB use series wound motors the will run the 
same direction regardless of electrical power polarity.  Reversing 
rotation of these motors requires swapping the field wire connections 
inside.  These motors usually have two black wires, and it doesnit 
care which is power or ground.

Later MGB motors have colored wires and will change direction of 
rotation if you change electrical input polarity.  I don't remember 
if they may be parallel wired with a phase winding, or perhaps have 
permanent magnet field magnets.  The carbon brushes are much the same 
and can be installed with the same techniques.  Pay attention to 
color codes for plugging into power, as reverse running greatly 
reduces the air flow output.  The cage fan should rotate with the 
sharp outer edge of the fins going forward to throw air out and 
forward faster than the fan rotation speed.

Barney Gaylord
1958 MGA with an attitude
http://MGAguru.com


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