Valeo alternator
 

I need some advice here. I just bought a new replacement Valeo alternator for my
'77 S. The outside diameter of the rear of the new unit does not fit inside the mounting ring on the fan housing,(Where the bolt holes are) and the bolts barely reach out of the holes-- WTF ?.
The fan housing is marked 901 106 101 5R .
Has anyone come across this problem before?

I recently replaced the alternator in my 1975 911S with the replacement Valeo (with voltage regulator) and it went smoothly. My fan housing has the same number as yours.

Did your old alternator have a spacer ring between the alt body and fan housing? If so, you won't need it with the new alternator.

Maybe it's just a matter of rotating the alternator because the bolt holes are not evenly spaced?

The bolt holes line up okay, and the Valeo slides in about 75% no problem then stops dead. There is a flange on the back of the Valeo that is the problem, it seems to be about 2mm larger in outside diameter than the inside diameter on the housing it should slide into. The housing is from a '74 though, as was the old alternator. (Now I'm thinking out loud), does anyone know if Porsche fiddled with the housing dimensions between '74 and '77?

Perhaps my experience will help. I ended having my alt rebuilt.


http://forums.pelicanparts.com/porsche-911-technical-forum/572956-alternator-question.html

Some fan housings are more shallow than others. I've taken some to machine shops to remove the excess so the new alternator fits. Now I take the defective alternator to a local shop and have it rebuilt so I know there's no issue.

http://forums.pelicanparts.com/porsche-911-technical-forum/294579-mid-9-upgrading-alternators-regulator-compatibility.html

Looks like 1975 and up fan housings were machined deeper for larger alternators.

Yup that's what I was thinking (after the fact of course), thanks guys.

See post #12 for a chart showing the range of 911 alternator dimensions:

http://forums.pelicanparts.com/911-engine-rebuilding-forum/664115-vertex-alternator-housing.html

+1 on Driver X' comment - have your old unit rebuilt (hope you did not core it). Folks should take this advice to heart - you'd be surprised what a good local electrical shop can rebuild and these units can be pretty hardy. As a backup, or possible sale in our classifieds can yield decent profit after having it rebuilt.