Vanagons are getting pretty old now. Expect some uncommon issues to crop up, like metal fatigue. Check your alternator bracket and tension arm. Does the alternator shake around a little? It may be cracked or a stud may be broken off, which will eventually crack the bracket. If you don’t address it, eventually you’ll hear a big noise while driving and see a red light come on the dashboard. You might also see a red light in your rear view mirror which would be your engine compartment on fire. The alternator’s power terminal runs straight to the battery and will discharge it through whatever metal the alternator is laying against. So, check the bracket and studs holding it on.
The tension arm may also be cracked where it meets the engine block. This isn’t as critical but contributes to allowing the alternator to flex the main bracket.