You can usually obtain a wiring diagram 'online' just by typing in the brand of AC you have and going to a site that has Dometic AC's. Of course you will need the Model # after you get there - but I don't see you having much problem chasing down a wiring diagram after some investigation on the web.

As to wiring the motor separate. Sure, you can run a separate electrical line (needs to on a breaker to handle the amps) just for the fan, but the problem would be 'cycling' the fan. For example: presently your fan goes 'on and off' by the thermostat. But if you wire your fan on a separate circuit - you would need a way to cycle it - and you would want to cycle it with the rest of your AC. You could always install a 'on/off' switch somewhere in the RV where you could manually turn it on and off - but I would think that would be more trouble than it was worth.

What you would need to do - is to wire the motor into a separate "relay" which would be controlled by your thermostat. Here is where it get's "sticky" cause you need to know a little about electricity in order to make sure you - dot all the i's and cross all the t's.

If you are pretty good with electricity then you should be able to get a 'relay' where the 'coil' (in the relay) is the same voltage as your thermostat - and then wire the relay so it will (via the thermostat) control the "line voltage" to the fan.

If you are not (good with electricity) I would obtain the help (hire someone if you have to) of someone to assist me.

Even if you have to pay someone - you're looking at a small outlay of money. I would venture to guess - parts and labor of $150 if he/she is fair.

hope this helps