The other day, some unknown jackass broke the side view mirror assembly off of my car. It was just dangling there by the power cord. Since I really do not want to spend $150+ on such a minor repair, I’m attempting to repair it myself. First, I cleaned both the mating surfaces thoroughly. The surfaces were smooth, so I scratched them up a bit using sandpaper. I then applied JB Weld epoxy, duct taped everything tight, and am now waiting for the adhesive to cure overnight. Will this work? Has anyone had success trying something similar?
I have epoxied both side mirrors on my mother’s Saturn (she broke one, neighbor broke the other). One repair is a year old, the other is going on two months. No sign of a problem from either, though they are a bit uglier than the stock arrangement.
This was with plain epoxy, not JB Weld, but I bet your results will be the same or better.
ETA: Her mirrors aren’t powered, though. The driver side has an interior manual control, the passenger is externally manual.
As long as the power connection terminals are still intact or you don’t care if its powered, it should be fine. If it doesn’t work Replacement mirror assemblies are relatively cheap if you search on ebay. I had to fix one on my ex’s jeep, just for the glass, cost $15 dollars w/ shipping and when it arrived it took about 5 minutes, usually comes with a self adhesive strip. I put on some Loctite outdoor mounting tape to be sure. Sorry to hear some jackass hit it, it sucks.
Mine are ?? polypropylene ??. Everything I tried just fell apart.
I did get some special primer to react with surface first, which is supposed to make it possible, but I couldn’t get it to work strong enough for an external part.
I successfully repaired the rear view mirror on my wife’s Voyager after I misjudged the distance to the edge of the garage door opening. 
JB Weld worked great.
My grandfather knocked off one on an icy driveway. He had the guy at the auto shop use screws and reattach it. It was around 10 dollars to do. It’s held up well for three or so years.
Update: it worked! Glad I was able to fix this myself while paying only a small fraction of what I would have if I took it to an auto shop.