This information might be useful for other Southwind and Pace Arrow coaches of this vintage. With a little help from ga traveler @ irv2.com getting started, I was able to replace the fan motor. I also found out since my original post that the in-dash AC/Heater unit is not made by Evans. It is the factory unit installed by GM/Chevy when they built the P37 chassis for Fleetwood.
Here are some of the details for replacing the in-dash AC/Heater blower motor.
1a. I pulled the glove box just to get a little more operating room. The easy way is to compress each hinge bracket one at a time while pulling the box and hinge pin forward. A brake adjustment tool was just right this job.
1b. Before you tear everything apart, you can verify that the fan motor is the problem and not some other electrical item in the circuit. Looking in through the glove box, you can see the white(gnd) and black(+12 vdc) wires. Using your voltmeter, verify that there is +12v or where the black wire connects to the spade lug that is mounted on the motor. (Key on, fan switch to hi, Vent) You can reach the spade connector because it is above the ground connector. If there is 12v, then verify the ground is OK by measuring for any voltage on the metal motor case. (Scrape off some of the paint to get a good connection.) If the motor case has 12v or any substantial voltage, then the ground connection is not good and you need to track down the problem in the ground circuit(white wire.
2. You access the fan motor from inside the coach by removing part of the kick panel that is in front of the passenger's seat. Take off the big vent grill and pull out the smaller round one. I decided to peel back the carpet that covered the panel. The carpet piece runs from the motor box to the far right side and from the floor to the dash. The carpet was stapled to the 1/2 plywood so use you own judgement in removing each individual staple by hand, vs tearing the carpet away from the staple.
3. Once you get the carpet completely off, you can see the plywood access panel. There is probably a hole drilled to accomodate a bump on the back of the motor. Remove any screws holding the panel in place. The panel has an aluminum trim piece at the top that remains attached. On my coach, the panel was tight against the floor and the floor carpet butted against it. When you pull the panel forward so you can pull it down from the dash lip, it runs into the floor carpet and the right side trim panel. After thinking about it a while, I decided to cut the panel into two pieces right at the upper line of the big vent hole. You're kind of on your own to figure how to make the cut on the right side up against the side panel. I slipped a wide putty knife between the plywood access panel and the side panel to protect the side panel while sawing with a key hole saw.
4. Now you have enough vertical room to pull the panel down from under the dash. This takes a little jiggling and maybe pulling on the dash a bit. When you get the panel out the rest is easy. Just take the screws out of the fan motor and pull it out. The part number on my fan motor was PM 105 which a standard GM/Chevy item and was available at O'Reilly's for $15.
5. Now just put everything back together the way it came apart. I put an extra couple of screws in the access panel and I also put a short 1 x 2 furring strip on the far right side to give the panel something to mount to. It's probably just fine without the extras because it is only for a surface to mount the carpet. Use your own judgement in reinstalling the carpet. If you have a stapler that shoots the narrow staples, great, If not, you could also glue it back in place.
Thought I would get these details recorded while things were still fresh. If you have any questions I can help with, email me at firstname.lastname@example.org