The wrong alternator--why?

[s2per]

Somewhere in the past, the previous owner of my '86 Carrera installed a 75 amp SC alternator AND alternator housing. The alternator quit charging recently and when I received my new 90 amp alternator (the right one), it does not work with the SC housing; alignment issues, etc. A proper new Carrera housing is not cheap!

Was there any advantage to use an undersized alternator (and housing?) It's not a track car and the aftermarket sound system could use as much amperage as possible.

[john walker's workshop]

Lots of swapping done in the past 40/50 years. You never know what you're going to find these days. The 75A unit should work fine in most apps.

[mepstein]

Carrera alternator housings often crack, are hard to find used and repros are expensive, so they probably just replaced it with whatever they had at the shop or could find easily.

[47silver]

The depths of the alternators are different over the years. To make sure it fits i have the one removed rebuilt

[Walt Fricke]

You should be able to deal with the fact that your new alternator is deeper (because more powerful) by going to a machinist, who can turn the mounting surface in the fan housing deeper. There are specs out there (try searching), but by measuring old and new alternators you can determine how much to take off.

[john walker's workshop]

Did that on my shop lathe once. What a pile of chips! Can't remember how I got it attached to the chuck.

[s2per]

Thanks guys. From what I've read, the SC housings do seem to be less trouble prone. I'll probably swap out the 90A for a 75A and just reuse my housing.

[GH85Carrera]

Originally Posted by john walker's workshop

Lots of swapping done in the past 40/50 years. You never know what you're going to find these days. The 75A unit should work fine in most apps.

One of the reasons I always recommend taking the alternator to a local rebuild shop. No doubt the unit will go in, and the wire connections will be correct.

[pkabush]

Originally Posted by Walt Fricke

You should be able to deal with the fact that your new alternator is deeper (because more powerful) by going to a machinist, who can turn the mounting surface in the fan housing deeper. There are specs out there (try searching), but by measuring old and new alternators you can determine how much to take off.

If memory serves, the amount of material needed to be machined off is 13.8 mm
As Walt said there are are threads on this.

[Quicksilver]

"Hey! Lookie what we got's on the shelf!!!"

[Walt Fricke]

The guys who owned the auto-electric shop in my town had the temerity to retire. No other place in town to rebuild alternators.

[Jonny H]

Our alternators come with shims so they can fit all fan housings. 175A of goodness. Just saying...

[pavegeno]

Originally Posted by Jonny H

Our alternators come with shims so they can fit all fan housings. 175A of goodness. Just saying...

Been running Johnny's 175A in my 88. Working great. Used to have problems with the stock alternator not being strong enough to prevent the voltage from dropping down below 13 with the battery having to help. I have a Griff's a/c with two additional electric fan condensers and lots of plug in electronics. My voltage never gets below about 13.5 even with headlights/fog lights on at night.

[ian c2]

Originally Posted by mepstein

Carrera alternator housings often crack, are hard to find used and repros are expensive, so they probably just replaced it with whatever they had at the shop or could find easily.

What area is one to inspect for cracks ?

[Jonny H]

Originally Posted by ian c2

What area is one to inspect for cracks ?

I made this video - it shows the machined area in question.

https://youtu.be/P9dy5wSbeHk

[mysocal911]

Originally Posted by s2per

Thanks guys. From what I've read, the SC housings do seem to be less trouble prone. I'll probably swap out the 90A for a 75A and just reuse my housing.

Remember, the Valeo 90A has 5mm studs versus the Valeo 75A which has 6mm studs.

[47silver]

I believe a guy who owned a alt repair shop still rebuilds them. If interested i will inguire

[s2per]

Thanks again guys. I've got my 75 Amp alternator at a local shop for assessment and estimate of rebuild costs.

[ian c2]

Originally Posted by ian c2

What area is one to inspect for cracks ?

Originally Posted by Jonny H

I made this video - it shows the machined area in question.

https://youtu.be/P9dy5wSbeHk

Thanks for the video .
Of the models susceptible to cracks , what is the thickness of that area ?
(I’m taking it that the thickness is the issue , so please correct me if I’m wrong)
The reason I’m asking is to understand what causes the break .
If all housings are the same depth throughout the years , the figures in that chart don’t add up ……
Also , when designing the updated alternators did you make a revised chart showing 964/993 info that you can publish for future reference ?
Maybe it is part housing , part alternator , part slipping belt ?
Ie : failing bearing catches , or belt slips then instantly grips adding torque & tries to twist the housing … (think drill bit catching and wanting to turn the drill motor in your hand )
I’m wondering if the spacers used on the inside to push out alternator to right depth could be redesigned and also be installed on outside of housing to act as a brace ?
These parts are now getting unobtainium , with used parts and aftermarket copies getting more expensive by the day , so I’m thinking the guys on here can maybe come up with a pro-active solution to future failures ?
.

[Mark Henry]

Member mb911 used to weld and repair fan housings. Send him a PM.