The lights on my ceiling fan were blinking on & off. I removed the housing and one wire was loose in the wire nut and was arcing with the movement from the fan. I blew out the area with compressed air and tightened all the wire nuts and now it works fine. Scary to think of it up there arcing and not seeing it.
One possibility is that it is an old Hunter fan. The old fans (think 80s and earlier at least) had an open oil reservoir to keep the bearings and I believe the brushes lubricated. If the oil has been used up, the brushes might be worn and start arcing.
Update, which sadly isn’t very satisfying, mystery-wise.
We called an electrician, who took apart the top assembly and checked all the wiring. He also checked the wiring at the wall switch. He said it all looked great and nothing was wrong.
He didn’t have a good idea about what might be causing the problem, but since it’s been going on for a long time and we’ve now been assured by a professional that it’s not going to spark out and catch the house on fire, I’m going to chalk it up as “baffling but harmless.”
It wasn’t the fan. We have this projector thing that sits on my nightstand and projects a pretty star and nebula design onto the ceiling.
I didn’t consider that because we keep it turned off except when we’re using it. Apparently, though, even when it’s turned off it will occasionally and intermittently flash the pattern. I caught it doing it last night and was able to look at both the projector and the ceiling at the same time and catch it. Bingo!
I am really glad my ceiling fan isn’t shorting out. I have no idea why the star thingy flashes when it’s not turned on, but now that I know what it is, I don’t care. It’s kind of cool to get random harmless ceiling lightning.