Anyway, all sorted now, but my questions are - what exactly wears out on > alternators?
Not much - it's usually an electronics failure that kills them. In my experience most likely the regulator followed by the diode pack. I've never actually seen one with worn out brushes or failed bearings - although of course this must happen. Nor have I ever seen one with burnt out windings.
Is it just a simple case of the brushes, or is there more
> to it?
The problem is testing the electronics - you can check most diode packs fairly easily, but the only simple way to test the reg is by substitution. And it can be very difficult to find spares.
This one, AFAIK, is the original, and the van's done a shade
> under 180k - is mileage a good indicator of how long they last, or is it
> more to do with total engine hours, or just total physical revolutions?
> And does lots of stop-start driving accelerate the wear on alternator
> brushes (or whatever else it is that wears out), or not particularly?
> And how long can I realistically expect this one to last (do about 30k a
> year, stopping and starting on average about 65-70 times/day)? Would it
> have been a waste to go for the Merc-badged Bosch one that came with an
> extra year of warranty, or as I thought, would that have just been > wasted money?
Personally I'd have looked for a good name re-con. Although if it's an unusual type this could also be difficult. Most decent motor factors or accessory shops can supply to order. They tend to be about 1/3rd of new Bosch prices.