Another question about roof-top AC's

I'll post again tomorrow but I think I figured out the problem. Yesterday after digging through the pile of paperwork that came with the RV I found the Dometic AC installation booklet. The booklet described in detail how the various controls work. After comparing how the controls on the thermostat worked and how they should work, I determined that my low fan speed circuit isn't working (there are 4 settings Low, Med, High and Auto). The low fan speed is the fall-back speed that Automatic uses during times of low system need requirements (such as in the cool of the morning). I set the system fan to run continuously on medium all day today while I'm gone and this evening when I return I'll check out why the low fan speed isn't working. I'm hoping it's something simple like a dirty or loose connection. I suppose it could also be a fan motor that's wearing out and no longer has the umph needed to start at low power (maybe an inline capacitor is needed?).
Steve