Pep Boys got to looking at the Astro and the mechanic said I should come down and have a look, so I walked the approximately 3.6 km to Pep Boys. It was cloudy and cool, which was nice until it started drizzling, which was less nice. The rain cleared by the time I got to the shop, and the mechanic showed me the multiple issues. This is probably the proximate cause of the serpentine belt falling off: the bolt holding the alternator in place worked itself loose. Now I know this particular bolt/bracket, because I replaced this alternator a few years ago in the misadventure when the previous alternator seized and caught fire. However, I suspect that what happened here is that the shop that worked on the air conditioning loosened the bolt to remove the belt when they were working on the air conditioning and not only did not put it back properly, but I think they may have actually replaced the bolt with one that was too short. That's because the oil filler pipe is also supposed to be attached to this bracket, and instead of being attached there, it was just hanging loose. He demonstrated that if he put it back where it should be, the bolt would not be long enough to hold everything in place. While annoying, this isn't insurmountable, as it just needs to be replace with a longer bolt. However, while this is probably what caused the problem, it's not the only issue. Because the oil filler pipe wasn't correctly replaced, the pipe worked itself loose from where it empties into the engine, and the grommet that seals the area was gone. Again, not impossible to fix, although it might be a little tricky getting the right grommet. More troubling, even though it wasn't the immediate cause of the problem here, is the power steering pump. It's difficult to see in this photo, but there is a crack in the pump bracket edit: pulley. While it is not immediately failing, it's impossible to tell how deep the crack goes, and it could fail catastrophically without warning. If they can find a replacement pump assembly, they can replace it in a few hours. If they can't find the part, they're willing to do the other work that needs doing, but I have to waive all warranty on everything due to the crack in the part. The alternator turns freely, so it does not need to be replaced. The serpentine belt tensioning pulley appears to be sound. But a new power steering pump and some way to fix the issue with the oil filler pipe, plus the incidental replacement of the bolt that holds the alternator and oil filler pipe in place, needs to be done, along with some other things. I also said to go ahead and replace the serpentine belt just in case, as whatever trauma was done to it while the alternator came loose and the belt fell off isn't worth worrying about. (I'll keep the old belt as a spare. Also, we're going to have to come up with a way to handle a field replacement of a serpentine belt, because this is not the first time we've had this happen.) Labor is not really an issue. It's annoyingly complicated due to the cramped nature of the engine compartment of an Astro minivan, but otherwise straightforward. What may be challenging is getting the parts. Pep Boys says that if they can get the parts by EOD today, they can have the van ready to go by EOD Tuesday. They'll see what they can find. I've already booked another additional night here at the hotel, and they aren't that busy, so more nights are possible. I'll let my management know what's going on and fortunately I really do have quite a few days of PTO in the bank, so the Worldcon trip is not imperiled. The cost is likely to be above $1000. My credit cards can cover it; that's one reason I carry an Amex Blue card with no balance and no annual fee. Let's just hope I didn't too any other harm driving the vehicle without the water pump between the time the alternator belt fell off and the battery failed entirely.