My dad did something similar this summer when the dash air in the RV died; the interior of the RV has mains-powered roof air, and he had a gasoline generator, so he rigged it up so that we could run the generator while the RV was moving in order to run the roof air, which is basically a small domestic air conditioner.

It doesn't do so well with steep hills, though; the generator is meant to be level while it's running.