x3 "mirror heaters..turn it on for a few minutes and touch one of the mirrors" On our Winnebago, they are wired to the Ford chassis and only work with the ignition on.
Ken
2006 Winnebago Outlook 29B E-450. 2012 Honda CR-V AWD Blue Ox Aventa LX tow bar and Brake Buddy Vantage.
There's a reasonably good chance that they might operate even with the ignition off, so it would be a good idea to make doubly sure you turn them off after use lest you run down the chassis battery in pretty short order.