Heater Fan Motor Demystified

I needed to see if I could get my fan motor rebuilt. Most DC motors are fairly simple so I decided to disassemble one to see what is repairable / replaceable by me.

This motor says it is from a 68 A-Body

A markings on the side read:
12V 15290-01
2837678 1558

build date??? 1558 155th day of 68????

Fan fully assembled








Loosen set screw and the fan came right off



2 nuts and the mounting plate comes off. Note orientation.



There is a cardboard gasket of sorts that comes off next.



Remove 2 more nuts and the bolts that hold the 2 halves together.




Continued...

Part 2...
Seperating the 2 halves.
Due to where the wire insulator is, it needs to be released before the halves are separted.

Carefully press in a dull screwdriver while rocking the insulator to the side and in.

Alternately rocking the shaft side half allowed the halves to be seperated. Go slow you don't want to damage any wires.




The shaft half off, a little steel wool on the shaft will help it come off easier



There is a small plastic washer, don't lose it.


Here is a shot of the fiber board that holds the brushes. Note the 4 twisted retainers



Brush plate removed, don't lose the springs.


To remove the armature, I had to move one of the wires that are crimped to the brushes out of the way a little


Armature came out no problem, the short shaft end has 2 plastic washers


Cont...

Part 3...
Looking down inside the lower half you can see the bearing and the windings. Everything looked good so I reassembled the motor, put a little lube on the bearing surfaces. The motor spins more freely now.



It looks like if the bushings are worn out, the 3 rivets would need the be removed, and the bearing retainer removed and replaced.

I suspect the windings can be removed as well, there are some positive stops on the side, but I did not want to do any damage to the motor so I did not try. A professional shop would have the proper tools and presses to do that.

From what I saw there is not much I could replace myself, the brushes, cleaning, polishing, and lubing would be about it.

Hooked the fan up to the car battery.
When it first started it pulled 4.1 amps but slowly sped up and finally got to 3.2 amps. The lube on the bushings probably got spread and the bushings may have heated up and expanded a bit.

I was able to confirm a long held belief that a fan cavitating draws less current than when it's moving air, and a baffle in front of the inlet to the fan, even 2 inches away reduces it's output noticibly

You can also chuck the armature into a drill and with very fine sandpaper like 400 grit on a flat stick you can polish the commutator smooth.

The patina on the commutator is fine. Removing it, will lead to brush wear again. Commutator patina is essential for less brush mechanical resistance and long brush life.