Here's another look at the old motor in place. The fan would barely turn by hand at all.
This is the replacement motor ("installed but never used", per the description from the seller), with the radiator fan blade from the old unit attached. Lisa pulled the fan off and washed years of grime off before attaching it. Whereas the fan wouldn't budge on the old motor, it spun freely on the new one.
With the AC cover removed, Lisa took to cleaning out as much dirt and dust out of the unit as possible.
She used the leaf blower to blow any loose dirt out of the unit. Some heroic dust bunnies flew away and took to the skies.
When Lisa first tossed this stuff down, I thought it was a dirt-encrusted cover. No, Lisa told me, it's just dirt. Many years of accumulated dirt on the condenser that she peeled away. Without all of this dirt blocking the condenser, it should work much better.
With the unit cleaned out, Lisa tried to remove the old motor. This was much more difficult than expected. The motor sits between the radiator fan (shown in one of the photos above) and a "squirrel cage" fan on the condenser side. To remove the motor, you have to disconnect a small screw that secures the squirrel-cage fan to the motor shaft. Except she couldn't get at the screw. It's inside a sub-assembly that defied her attempts to access it, and scraped up her hands for her efforts.
Normally, I'm not a fan of instructional videos, but in this case I'm glad that I was able to find this video about replacing the motor on a similar unit, which gave us the hint needed to get at that blasted screw. Even then it's something that makes one nervous, because you're twisting the metal pipes that hold the AC coolant, and if they break, it's game over.
Eventually, Lisa was able to work the holding screw off the squirrel-cage fan, remove the old motor, and fit the new one into place and re-attach the holding screw. After that, she very carefully moved the condenser unit back into place and secured it. Then came the second-most difficult part: the wiring.
Lisa took this picture of the wiring before starting work and had me print it for her to use as reference up on the roof. These wires run to the fan motor (out of sight to the left where the wires come together) from the starting capacitor, thermal cut-out, ground, and on to the controls down inside the trailer.
As rather expected, the wires on the replacement fan are not long enough, as it was cut out of a salvaged unit. Lisa thus had to strip and splice wires, securing them with wire nuts. We did not get a photo of the result, but I reckon it's a bit tidier than the original. I'll try to remember to ask her to get a photo before she puts the top cover back on the unit.
With the motor back in place, the fans secured, and the wiring done, it was time to try the acid test. Lisa came down from the roof, plugged the power back in (everything was unplugged while she was working on it, of course), and turned on the switch. The fan immediately sprang to life! Then she cut in the condenser and waited a few minutes. Cold air!
We're not completely finished, but after putting away all of the tools and doing initial tidying up, Lisa was completely beat, and I don't blame her. All I did was sit in the shade and fetch tools when needed. (Lisa was in the shade as well, from the carport shelter. Also, it was cooler today, with the air temperature only 27°C in the shade rather than ten degrees hotter like it was last week.)
The swamp cooler will stay in place until at least tomorrow. I suggested that Lisa run the tank town all the way. (Swamp cooler pump motors are designed to run dry without harm.) That way it will be easier to take down, as the cooler is very light without any water in it.
I plan to see if we can have the existing motor rebuilt, as we assume it's either the bearings or the windings, and it would be good to have a working spare should this one give out. It's hard to complain too much about how long this one has lasted: 25 years.
Should everything work as planned, we'll start the rest of the clean-up and tear-down, and box up the swamp cooler and clear the "ziggurat" of pallets in the carport tomorrow or over the weekend. I'm really glad this worked, and that we were able to work around the problems until the part arrived and Lisa could make the repairs.