azteca,
Your coach is old enough that it could just be a type of converter referred to as a Buzz-Box. These were regulated by being tuned to the 60Hz line frequency. They provide a very stable output voltage. There is one problem, most were set up to provide 14.4VDC. That is real good for the lights and stuff, but it will destroy batteries in relatively short order if you leave it on.
Why don't you read the tag on it and come back. In the mean time, leave it online only long enough to get a good charge on the house.
Matt
