Use later alternator in early 911?

[KevinG]

I am wondering if it is possible to replace my existing Bosch 55 amp alternator (dead) with one from an 84-89 Carrera. I gather that there are wiring differences due to the internal regulator, but have heard that there are ways to re-wire. Are there any other problems with making this switch? Car is a 72 911.

Thanks!

[sc_rufctr]

I installed an alternator from an 84-89 Carrera in my 78 SC.. Worked great but you're right there are wiring changes but it was so long ago I don't really remember what they were. Must have been simple because I did it on my own...lol...

I can't see any drawback or reasons not to do it.

[RoninLB]

ps: I didn't have to change idiot light bulb to 4 watt with Valeo alternator. Above is for Bosch alt.

[304065]

Kevin, if you search here you will find a lot of information about this. But to summarize:

1) The later alternator is longer which requires a different fan housing;
2) The later alt is internally regulated which requires a small modification to the wiring; and
3) the internal reg heat soaks from the hot engine, causing it to occasionally not work and fail after a couple years

[47silver]

went through a lot of alternators last year to find one that worked.

the depth of the alternator is critical or the fan will hit the shroud.

they look similar but there is a 1/2 inch? or so difference which will cause problems..

when you remove the old one
measure distance from tip of the shaft to the base of the alternator, there is a pic on here somewhere of the alternator differences.

[RoninLB]

I considered a marine digital external regulator if I had a cooked internal regulator problem.

Never the less I take care as best I can to prevent hot shut downs and letting it cook.