Flex-a-lite fan issues, lessons learned
I don't know how common these Flex-a-lite electric fans are on AS motorhomes, but my 83 310 diesel has one and it had died. The PO apparently didn't know this. It wasn't that old -- about 8 years since install and less than 20K miles -- but roasted. I learned a bit in the process of figuring this out that I thought I would share.
When I got this coach it was with a toasted engine due to coolant loss (number one lesson: don't use PVC fittings on heater hoses!) It still ran and I was able to have it rebuilt in-frame with factory parts. It seemed to run cool enough, the PO told me the electric fans never came on (and that the manual fan switch didn't work). There was no engine-driven fan. Driving it from Seattle to central California caused no undue heating so I thought that was okay. As I started to pull out some of the electrical rats nest in continuing the restoration, I found that both fan motors were seized up and at some point in the past, the wires, fuse holder (which had a blown 30 amp fuse in it) and part of the controller had melted.
This is a Flex-a-lite 220 system, with two 12" fans producing 2500 cfm, and is priced at around $475. Summit Racing has them for $216 with free shipping. The system draws about 20 amps (10 amps each fan).
The fans are supposed to be wired in parallel with a (supplied) tee connector. This is really dumb. If one fan motor shorts out, it will blow the fuse, rendering the other fan inoperable. So, first modification was to skip the tee splice and bring the individual fan wires up to the front and fuse them individually.
Now, if one fan fails shorted, the other can still operate.
I don't trust the controller box in high heat conditions. The traces to the relay are less than 1/4" wide and all of the power goes through a single push-on 1/4" tab connector. 20 amps through a 1/4" wide circuit board trace of 2 ounce copper will cause a temperature rise of about 175 degrees F. On a hot day it might be 160 degrees under the hood, that means 335 degrees on that trace ... and the solder melts at 360-375 degrees. But it's easy enough to install it so you can bypass the controller if you need to. The manual fan switch does not bypass the controller; it just operates the same relay that the thermostat does.