My 73 144 needed a heater motor changed when I bought the car. I removed enough of the under dash parts on the right side to allow me to get the right side housing apart. From there I could see I would be repacing the motor and that one that was insalled was the original factory style. The replacement units are of the later permenant magnet type and involve the installation of a new switch and resistor as well as the motor being replaced. I proceded to remove enough of the shrouding on the left side to enable me to get the left side housing off and the old motor out. Not the easiest job in the world but in my mind this was a saving in time from the removal of everything. I bought the replacement motor from a jobber type establishment up here in Canada ( Canadian Tire ) for about $55.00 and got the switch and resistor from a friend who has a 240 sitting around. A slight bit of grinding is nessisary to facilitate the installation of the housing of the new motor. Good luck.

Get the orignal replacement motor if you can. I just finnshed replacing the heater motor in a 73 with the newer type 4 speed kit. The kit cost about $60.00.
Becuse I installed the kit, which requires some modifing the case by filing with a rat tail file. This in return meant that I had no choice but to remove the dash so I could remove the heater. The actual modification didnt really amount to much work (becuse I had the heater out of the car). Heater motor repacement on a 73 or newer isn't a job I would ever want to have to do again. The 67-72 heaters are a snap to remove amd replace in comparison. The 73 dash is made up of about 12 different parts, getting at some of the screws is miserable, and it is even worse putting them back in. No wonder the fellow who sold me this car was so happy. If I knew it would have been so much hassel to fix the heater, I would have passed on buying the 73. Any way I did end up with a great car at a cheap price. In the end it was worth it. Good Luck

69-72 is easier than 73-75. (That is one of the reasons you check the
year rather than saying "ALL") The later ones have a lot more dash to remove
and a more complex heater with more stuff on the back side.
It sounds like you probably have gummed up bearings, perhaps accompanied
by worn brushes.
DON'T try to run the motor any more until you do something about it,
and maybe you can save it. Continued attempts to operate could result
in burning the windings from excessive current.
--
George Downs, The "original" Walrus3, Bartlesville, Oklahoma