I recently upgraded my heater blower motor in my 77 CJ5 Jeep with a blower from a 90 blazer. Attached are the steps I did to accomplish the upgrade:
1. I did some research to determine which motor would work for this upgrade. The motor I used was a 90 blazer PM 141 - It has a 5/16 shaft close to 2" in length, and turns CCW. (You determine the direction by looking at the shaft and the direction of rotation not the back of the motor)
2. I then verified the rotation once I purchased the fan by connecting my battery charger to the electrical prong and the ground on the shroud.
3. I then determined how much gap there was between the new motor and the old fan shroud or fan box cover. My measurement determine approximately 7/8".
4. I found a ¾ " thick board and a 1/8" piece of panel board in my garage that was perfect for this.
5. I measured the widest area on the motor that tapers until it is square’d off on the motor and made a circle on the panel to cut the hole with a jiz saw.
6. After cutting the hole I made sure that board would go over the motor and then I drew out the shroud on the panel and cut it out too along with a small protrusion from the motor electric prong so everything would fit square. .
7. I used the panel as a template and cut the ¾ in board out too.
8. I then determined that the old metal shroud would need to be modified too for the motor to sit square. I measured the new motor and cut what I needed out for the motor to fit securely. There were two protruded areas on the motor that I had to cut gaps out of the shroud. I also made sure that the air vents were opened up to make sure the motor will keep cool. (grinder worked and fine tuned with a file)
9. I then clamped everything together to make sure everything matched up good. Once everything was together, I drilled 4 holes and installed 1 ¼ " bolts with locking nuts. (make sure this does not interfere with the fan squirrel cage, I put these bolts on the outside edge of the cage.)
10. I then fit it up to the heater and made sure there was clearance throughout and put the juice to it. Perfect blows big time - exactly what was needed.
11. I then took everything apart, painted it black, and made a home made gasket between the motor and the original shroud making sure the holes were opened so the motor can keep cool.
12. I also put silicone between all boards and the original fan shroud on the wood side.
13. Bolted everything back together and painted again. (make sure to put tape over the vent hole and cover the electric prong.
14. I have ordered a 3 way switch with a built in resistor.
Hopefully this will help you or give you some ideas - Good luck!!!
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