Do the alternator and VR have to be matched??

dtw · 12-20-2003, 01:26 PM

I've got an early SEV Marchal alternator installed, and an SEV Motorola voltage regulator. The alternator light is remaining on, and the voltage across the battery is increasing to over 15V with increasing RPMs. Questions-
-Is the VR just bad, or is there some incompatibility with the alternator?

-If I swap the alternator out for a later 55 amp Marchal SC variety (external regulated), do I need a different regulator?

Lorenfb · 12-20-2003, 02:04 PM

The regulator and alt. don't need to be matched. The later SC type
of Marchal alt. is 70 amps (the best ever Porsche alt. except 996).

There are two possibilities for your system charging to 15 volts:

1. The voltage reg. is bad, or
2. The field diodes (The three that feeds the D+.) are open
or at least one is.

If you have the early alt. with the red plate on the back
(one of the worst alt.), then problem is the reg. since
there are no field diodes.

Have Fun
Loren
'88 3.2

gjp1960 · 05-25-2004, 07:43 PM

I have a similar question.

I just ordered a new voltage regulator, described in the catalog as "Voltage Regulator, external (for Motorola 70 amp alternator)" with applicable years listed as 1971 - 1974. My car is a 1973 with a Marchal red plate alternator.

Will they be compatible? I don't know if how many amps the Marchal actually puts out. If it is less than 70, will that cause problems?

Thanks.

Lorenfb · 05-25-2004, 10:02 PM

The key is that the regulator does not allow the battery voltage to get over 13.7
volts. The red plate SEV is a very weak alternator (55 amps) and as sure can be
easily destroyed by huge batteries and high voltage regulators (> 13.7 volts).
As long as the regulator doesn't cause excessive charging, it'll be O.K. The
old style (removal metal cover) can be adjusted to the proper voltage.

gjp1960 · 05-26-2004, 09:12 AM

Whoa, this is the first I have heard about adjusting the voltage regulator. How can I tell if mine is adjustable? How do I adjust it?

The external regulator in my car now is an SEV Marchal 14v unit. It is rectangular (2.5 x 1.5 inches), dull silver in color. On the back are three rods, threaded, which I thought seemed kind of odd. I have not tried opening it up to see what is inside, but now I think I'll have to. Especially if I am replacing it anyway.

Thanks for the help!

Greg

Early_S_Man · 05-26-2004, 10:03 AM

Greg,

The three 'rods' are not threaded ... they are wirewound power resistors and what looks like threads is actually turns of Nichrome resistance wire ...

gjp1960 · 05-30-2004, 05:08 PM

Hi again - I took the cover off of my voltage regulator and took the following photos. This is not at all what I expected to see in here!

The first thing I noticed was that there is no separation between the upper and lower contact points. I assume that the unit works by pulling the arm down to make contact with the lower contact point when the electromagnet gets enough juice going through it. Do I adjust the screw and raise the upper contact? Is the spring another adjustment device?

I have not made any adjustments since I removed the cover. Nothing seems to be loose, just no gap in between. Any help you can give would be appreciated.

Thanks!

Greg

[IMG]C:\My Documents\Voltage Regulator 1.jpg[/IMG]

[IMG]C:\My Documents\Voltage Regulator 2.JPG[/IMG]

[IMG]C:\My Documents\Voltage Regulator 3.JPG[/IMG]

[IMG]C:\My Documents\Voltage Regulator 4.JPG[/IMG]

gjp1960 · 05-30-2004, 05:13 PM

OK, I guess I don't know how to post a photo either.

From the description can anyone help me figure out the proper way to adjust my voltage regulator?

Thanks!

gjp1960 · 05-30-2004, 05:19 PM

Here we go...

Lorenfb · 05-30-2004, 06:07 PM

You adjust the tension on the spring.

More = higher voltage

david914 · 05-30-2004, 06:29 PM

I might be seeing things, but in his pic the voltage regulator contacts appear to be too close together. In other words, the normally open and normally closed contacts are both touching the common at the same time. That would cause some problems.

gjp1960 · 05-30-2004, 07:21 PM

David - You are correct, they are both making contact. I disassembled it and scraped some debris off, and now there is a little travel room (maybe 1/64 inch) between where it makes contact with the upper and lower points.

Do you know how much travel there should be? It appears that to adjust this I will need to bend the upper or lower arm just a bit.

Around the contact point where the debris was, there was a little discoloration, as though it had shorted out. I'm guessing that was the origin of my problem.