alternator trouble

[richtbiscuits]

Hi. Looking for a little help regarding the alternator on my 412LE please.

Driving home the other night I heard a sudden noise which was shortly followed by a dry scoring noise, rather loud. I had all gears and the engine got me the quarter mile home. On inspection in the engine bay I found a loose alternator pulley without nut and washer which I found on the tinware under the fan. The screw thread on the alternator shaft is gone, ground away, as if the alternator has locked up. On removing the belt and pulley the alternator rotates freely in both directions. I found a long piece of cable tie under the fan too but it is free from damage and I suspect it was from where the oil filler rubber was tied to the filler tube. Could the cable tie getting caught cause the alternator to lock up and strip its thread almost instantly? The only other thing was I changed the battery 5 or 6 days previously and connected a brown/white wire to the battery earth strap which was previously not attached, other wires were taped but not this one and the connection seemed obvious. It was driving fine but have I done something stupid?

Either way the alternator needs replacing. I have a 55 amp fitted but the manuals list three different types: 35 amp, 45 amp and 55 amp. Which is correct for a W coded 1700 FI engine? Anyone know where I might get one? I see there are 55 amp alternators for 1700, 1800 and 2000 cc bus available so will this fit my engine? One add recommends changing the voltage regulator too, is this necessary?

Lots of questions, I know, but auto-electrics confuse me no end. Any help or advice is greatly welcomed. I've only had the car one the road for a couple of weeks and it was going great guns.

Thanks

[937carrera]

Seems very strange, do you have any photos ?

As for the alternator, if no=one has a spare on here then try ebay or look around for a local auto electrician who can refurb / swap for yours. Try searching by the Bosch part number for cross references as well, the original part number is 021 903 023FX, which I suspect you already know as VW Heritage are advising changing the voltage regulator

I would go for the 55A version - the LE needs additional power for the computer compared to the carb cars and bigger is better

[937carrera]

Could be helpful:

http://www.thesamba.com/vw/forum/viewto ... 01&start=0

Table of Bosch part numbers and equivalents

[richtbiscuits]

Thanks for the advice. I suppose the stripped thread could be from the pulley spinning, unattached, on the alternator spindle. The woodruff key has disappeared and I suspected it has passed through into the fan housing and/or heat exchanger. I thought to get a 55A but it's good to have some further advice as to why. Perhaps the nut just worked loose with vibration and allowed the pulley to come free. It was torqued up but I might use two nuts when I change the alternator!

[937carrera]

If I recall correctly there isn't a lot of thread to go at. Make sure you get a new woodruf key and I suggest you use loctite to prevent the nut vibrating loose.

I see the alternators are a bit pricey. It may be possible, if the electronics are fine, for you to use chemical metal to replace / reinforce the remains of the threads and reuse your existing component - photos would help