Charging house batts while driving

The "Ford starter solenoid" style is correct, but note that the solenoid used for battery isolation is NOT the same as the starter solenoid. The isolation solenoid is rated for continuous duty, where the starter solenoid is only rated for intermittent duty. I don't recall exactly what the earlier Fleetwoods used for the solenoid trigger, but the two most common sources are the ignition switched tie previously mentioned or an oil pressure switch controlled source. The ignition switch is the more common connection though. I've traced problems with "house" batteries not charging while under way to a burned out intermittent duty solenoid that had been used as a replacement for the required continuous duty solenoid on several occasions over the years. Of course given the age of this RV, even a continuous duty could easily have died as well.