I don't know if this will still be relevant, but I was having the same problem a couple years ago. Motors were sluggish to start, and one would hang. I had to tap it to get it spinning. I ultimately bought the TYC 622210 7/9 blade fan unit and installed it. The specs on the box label stated that the components of the TYC unit were direct replacements for the 700W motors (and, obviously, the 7 and 9 blade fans. Rimmed.) Instant remedy of problem. The new fans spin up significantly quicker and move much more air. Almost two years on them, and they're still doing fine. Summer temps over 105* and pulling a grade coming home, and the temp needle never goes above the 210* mark. I kept my original fan assembly so I can source original motors and fan blades and have it ready in case the TYC unit craps out. I replaced the high and low speed relays, as well. I couldn't find the third relay at the time and forgot about it. They're still running, so I assume it's okay.