2oldman...Thank you for the learning encouragement. I don't believe this would be a battery problem. It has been going on for the 4 or so years we've had the motorhome, and we've gotten new batteries in that time.
wa8yxm...I have a digital multimeter. Your previous post mentioned "analog multimeter". Why analog? The clock is a panel built in to a little wood sort of cabinet. I have to unscrew 4 screws to get to the back of it. Clock does have "Display on/off" toggle switch. I don't know where to touch the black and red needles of the multimeter onto to check the voltage. I assume I would do that live (with clock on) while my spouse turns on the furnace?
beemerphile1...Good idea! As I noted before, I'm not too concerned about this issue. But I like a good puzzle, and this is just that. Unfortunately I'm not too handy at working this kind of puzzle, compared to, say, a word puzzle. :)