1970 911T, Alternator connections/questions

[on-ramp]

Are these connections correct:

Brown wire = D

Black WIRE = DF

DOUBLE RED WIRE = B+

BLUE WIRE = +/61


Also, what's this part of the alternator(says DF on it)?:



and should it look like that? one leg shorter than other?

there is also a short ground strap going from body of car to alternator housing is this correct? thanks.

[pwd72s]

one thread of many...if this doesn't help, you could search for more?

Alternator Install

[on-ramp]

i also have Marchal ext. voltage regulator (installed last year) but my alternator is a Motorola (original equipment)
can anyone confirm?

[pwd72s]

My thinking is that the Marchal and the Motorola external V. Regulators are functionally identical...I could be wrong on this, so hoping Loren or Warren weigh in...but I did get that info from a mechanic I trust, Jeff Gamroth. If you've ever read of ROTHSPORT built cars in EXCELLENCE, you know Jeff's a good info source.

[on-ramp]

Originally posted by pwd72s
My thinking is that the Marchal and the Motorola external V. Regulators are functionally identical...

thank Paul,

however there is a little gold sticker near the engine saying that " Alternator and regulator must be from same manufacturer".
and it's in 3 different languages.


is my original alternator a Motorola and therefore should i have gotten a Motorola regulator?

[pwd72s]

motorola/marchal should be interchangable...this according to the research I did when gathering up some spares. You might PM Loren & ask...he rebuilds Porsche electrical components for a living...I don't.

[on-ramp]

Originally posted by pwd72s
motorola/marchal should be interchangable...this according to the research I did when gathering up some spares. You might PM Loren & ask...he rebuilds Porsche electrical components for a living...I don't.

who's Loren? username on this BBS?

[304065]

Wire connections: WRONG!
there are FOUR

B+ (red wire, battery positive)
D- (brown, ground)
DF (black, Dynamo field, to brush holder faston tab)
D+/61, (blue, "pre-excitation current" from warning lamp pin #11)

You are OK, but make sure your brown goes to D- (you probably couldn't see the minus)

That thing is the brush holder (DF stands for Dynamo Field)
No, both brushes should be same length
You should have a ground strap from D- (case of alt) to one of the engine case parting lines.

The REASON for using the same manufacturer VR as alternator is based on differences in design, they need differing input voltages to the field to put out the same output voltage. You should use the same manufacturer, like the sticker says, unless you want to do some VR hacking. Do a search on "Lorenfb" or "Early_S_Man" or my name and the word "alternator" for more than you could ever possibly want to know about alternators.

[on-ramp]

john_cramer

yes, you're right, there is a little minus there, making it "D-"

however, the ground strap was connected to one of the 6 studs and to the engine case parting line.

is this correct of should this ground strap also go to "D-" on alternator? i also noticed this ground strap was secured ABOVE the plastic shroud and under the nut, not making contact with the alternator body.

[304065]

It depends on how long the strap is. Contact with the case, outside of the fiberglass airguide, is probably OK, but those are small studs. Mine goes inside, to the D- terminal on the alternator, like an M8 stud or something.

Good luck!

[on-ramp]

here's a pic of the copper round thing that contacts the 2 metal things (one is shorter than the other) sticking out the brush holder. hows the condition?

[pwd72s]

Originally posted by on-ramp
who's Loren? username on this BBS?

http://www.systemsc.com/

This is Loren...

[on-ramp]

anyone know where i can get that brush holder in the picture above?

[304065]

On-ramp, those copper round things are actually the "Commutator." Current flows from the DF (or D+/61 at startup) terminal through them, magnetizing the rotor, which induces an alternating current in the stator (the part that doesn't move), which is converted (rectified) by the diodes into DC.

Part of the rebuild process is they will "skim" the commutator by pulling the rotor out and chucking it up in a lathe. They then rotate it with the lathe and use a cutting tool to smooth out all the grooves in the copper, giving you a nice tight contact with the brushes.

Every brush holder I've seen has equal length brushes, I don't know why yours are worn.

Anyway, if you take the alternator in for a rebuild, they will do all that stuff for you. Make sure they don't convert it to an internal regulator or give you an "Exchange" unit that's a Paris-Rhone: tell them you want your 55A Motorola/Marchal back.

[on-ramp]

Originally posted by john_cramer
On-ramp, those copper round things are actually the "Commutator." Current flows from the DF (or D+/61 at startup) terminal through them, magnetizing the rotor, which induces an alternating current in the stator (the part that doesn't move), which is converted (rectified) by the diodes into DC.

Part of the rebuild process is they will "skim" the commutator by pulling the rotor out and chucking it up in a lathe. They then rotate it with the lathe and use a cutting tool to smooth out all the grooves in the copper, giving you a nice tight contact with the brushes.

Every brush holder I've seen has equal length brushes, I don't know why yours are worn.

Anyway, if you take the alternator in for a rebuild, they will do all that stuff for you. Make sure they don't convert it to an internal regulator or give you an "Exchange" unit that's a Paris-Rhone: tell them you want your 55A Motorola/Marchal back.

this is the alternator that was supposedly rebuilt last year, i paid $90 for that.

[pwd72s]

Loren would charge you a bit more than $90...you would also end up with a good alternator...