Last couple days I did a lot of reading about blower motors and conversions and such for 12V motors in the AD trucks (and some others). I read all about resistors and other methods of dropping the voltage... Except my old 6V motor is toast, and I don't mind a non original 12V motor if it is an easy swap, easy to get, and very functional.
Yesterday I took some of the part numbers I found mentioned and went to NAPA to see what they could get.
One of the restoration parts vendors sells a Unimotor 14504 04054 (from the picture of it) for near $60
Siemens PM354 is one option mentioned and Autozone list them for $28
NAPA gave me their part numbers: 655-1022. This one has 1/4" shaft and bushing for 5/16", will run either way depending on polarity, and is approx size as the original Delco in my original GM/Harrison recirculating heater. Cost $33 655-1020. This one is longer and has 5/16" shaft. Might fit the fresh air heater? Other than shaft size I think it would fit the recirculating heater I have too. Cost $27 The motor sticker shows VDO part number PM354, box has the NAPA number.
Attached, PICTURE of motors side by side
In my searching I didn't find many clear answers on what motor, hope this helps someone else in the future. And should save anyone about half the money for often the same motor from the online vendors.
I'll have more pictures as I get the heater back together.
More pictures attached of my heater
Grigg
Last edited by Grigg; 08/23/20175:43 PM. Reason: add pictures
Useful information Grigg. I wish I saved my research for an aftermarket Sears Allstate 6V to 12V heater motor conversion I did years ago. I do remember referencing the on center attachment bolts and shaft length and diameter. I also recall walking into a large electrical small motor shop in Richmond, VA's west end with my 6V motor, the guy walking out back and returning with a new 12V motor exact in size to my old 6V. Got to love those old shops in the larger cities.
~ Cosmo 1949 Chevy Half Ton Rocinante, like Don Quixote, he is awkward, past his prime, and engaged in a task beyond his capacities. "...my good horse Rocinante, mine eternal and inseparable companion in all my journeys and courses." ...Don Quixote, Cervantes "If you come to a fork in the road, take it."...Yogi Berra "Rudeness is the weak man's imitation of strength." ...Eric Hoffer
Just finished installing the shorter more expensive NAPA motor 655-1022. Wow was that easy! Absolutely zero modifications necessary, simple remove and replace. The two bolts lined up perfect, they were long enough and not to long, same with the 1/4" shaft.
Checked rotation on the bench and grounded the correct wire to the spare stud on the back of the motor.
Really really easy.
My truck is presently 6 volt positive ground, the 12V motor runs at what sounds like a "medium" speed. Later when I switch to 12V negative ground I'll unplug the wires and switch polarity, done.
That's the same motor we use on the fresh air style heater and install it in the 6 volt case. It comes with an adapter for the 5/16" shaft the other one uses. Good to know we can use the same one for both.
Something that might be of interest: The motor on our fresh air heaters is supposed to turn CCW. I do not know about the one you are working on, but switching the polarity of the motor is what determines the rotation. It doesn't care which is negative or which is positive other than that. The Orange wire on the PM354 is ground on the fresh air heater to get it to turn CCW. It's sort of confusing.
The new motor just slid right in the heater core/housing. I had read about slotting holes to make motors fit and at least with this combination that is completely unnecessary, just bolts in as easy as you please, zero modifications.
Yes the direction of the motor can be reversed by changing polarity (switching wires). Not sure why the motor tag specifies "clockwise" when it definately will run either way. I won't get into explaining which wire is grounded because for one reason GMC trucks were positive ground, so different answers for Chevy and GMC. Then if for some reason different heaters use a different direction fan that would change the answer again. Simple answer is "wire it so it pushes air out the vents".
The last picture you can see a little detail I thought of for the wiring. Used a male spade terminal on each wire. Then on one of the spare motor studs slipped a female spade "flag terminal" connector over it and clamped with a nut. Now just plug in one or the other leads as needed to ground and connect hot wire from heater switch to the other. This is simple and effective and most of all requires no tools to change polarity when I switch to 12V negative ground in the future.
To recap NAPA # 655-1022 ---1/4" shaft and bushing for 5/16", approx size as the original Delco in my original GM/Harrison recirculating heater. Cost $33 NAPA # 655-1020 --- 5/16" shaft and a little longer motor than the above, which may fit and is worth a try for the fresh air heater. likely fits a lot of these old heaters if 5/16" shaft size is OK. Cost $27 and is exactly VDO part number PM354 with a NAPA box.
Hope this helps someone else tackle a heater motor swap on a budget and clears up some of the confusion about different more or less suitable motors and what's required.
