TheSamba.com :: View topic - Alternator wiring--B+ or D+ for Red wire?

Wed Jun 23, 2010 6:03 pm

The red wire from the harness has a conector like it's meant to be on the B+, but the 1970 diagram says D+. Do I need to put a different connector on the wire and put it on the D+, I have a D and don't see a + there. Thanx!

Wed Jun 23, 2010 6:31 pm

A '70 would've had a generator in it from the factory, and that alternator is externally regulated. Where's the regulator?

Wed Jun 23, 2010 6:35 pm

under the rear seat. That regulator right? The motors actually an AE from 71, DP DR.

Wed Jun 23, 2010 6:48 pm

might look at speedy jims website and see if he has anything that might help you!

about 3/4 the way down the page Alternators/Generators
http://www.nls.net/mp/volks/htm/elec.htm

Thu Jun 24, 2010 7:23 am

Be sure you are NOT using the DC regulator from the generator. The alternator ext regulator is different.

This is a DC regulator for a generator:

I think this is a later model (can someone confirm?):

I believe there were a few types of ext alternator regulators.

This is what my Bosch regulator looks like:

The other Bosch model looks like this:

Or this Motorola model:

Thu Jun 24, 2010 7:53 am

B+ goes to Battery + and is the big red wire. All others are labeled and go to the corresponding terminals of the reg (same labeling).

Note: some regulators have a term called B+ and the alt/gen big wire leads to this term then continues on to the battery +.

Thu Jun 24, 2010 10:41 am

Ashman: yes, the first regulator pictured looked like what was regulating the generator on my '70 bug. The second one looks like the replacement one I put in (just to update). It appears to be more "solid state" than the original one.

Thu Jun 24, 2010 12:40 pm

hmm. very interesting. The new harness had green-brown-red that we're meant for the old generator and I simply hooked them up like Speedy Jim suggested(thanks JonF!)--Red to B+, green to DF, brown to ground. It made to generator charging light work correctly, but I haven't checked if it's charging the battery properly yet. I have a DC reg like the first pic, is it necessary that I get a seperate one for the alternator?

Fri Jun 25, 2010 4:44 am

Are you saying you have wired the DC regulator under your back seat to the alternator terminals?

Here are the pics from Speedy Jim's site:

Which one did you follow?

I've never tried this....

Fri Jun 25, 2010 11:07 am

I found a Motorola, is this one internally regulated? I think it may be. If so I'll just bolt in that bad boy.

Fri Jun 25, 2010 3:29 pm

Yes, that big white box on the top is the regulator.
The small spade connector is D+.

Sat Jul 03, 2010 11:48 pm

I wired my Bosh Alternator like the example in Speedy Jim, but I dont think I did something right.

Its a 60 with a 1776, and there was NO original wiring for me to go on.

Where does D+ go exactly???
I have it wired up to the ON of my ignition switch, but this causes the car to NOT shut off. (once running, power keeps coming up from D+ and back down through the ignition switch to the coil.)

Do I need to put a diode in to prevent this?

Sun Jul 04, 2010 3:18 am

The D+ has two functions,
It is the field wire that allows the regulator to "sense" the charge level of the electrical system.
It also provides ground to the Gen light when initially turning the ignition switch to ON.

You are correct that at the moment the ignition is turned OFF, the alternator will provide power to the D+\Gen light which is then connected to the ignition circuit at the fuse box. This could power the ignition, but the voltage that makes it to the engine compartment will be less than 12v+. In my car I measured 7v+ at the coil wire. For a 12v coil this is usually insufficient to make spark. Also, it probably won't keep the idle cutoff solenoid powered either.

Note: if you are like me and have a Bosch relay in the engine compartment, these only require 5v to remain closed. This relay would continue to provide power to the coil. I had to install a diode onto the terminal for the Gen light. This prevented the back flow of voltage beyond the Gen light.

Mon Jul 05, 2010 8:06 am

So Im still wondering.

WHERE does the wire from the D+ terminal, GO?

To the alternator light in my speedometer?
Or the ON side of my ignition switch?
Or????

Mon Jul 05, 2010 8:13 am

I found it elsewhere in the Forums!

http://www.mydune-buggy.com/home/dl_files/AlternatorBasics.pdf

It goes to the idiot light in the speedo, and can be bypassed with a Diode.

Sun Apr 01, 2012 4:13 am

erich777 wrote: I found it elsewhere in the Forums!

http://www.mydune-buggy.com/home/dl_files/AlternatorBasics.pdf

It goes to the idiot light in the speedo, and can be bypassed with a Diode. I understand that part? But? what about the rest of the information? The above link that erich777 provided was awesome. Considering the simple question? An replied, with a simple answer? Yo, I was just getting frustrated with everybody's information about the D+ wire goes. In my case, time was of the essence. Thanks to the both. Seller1

Mon Jun 04, 2012 7:06 pm

Hello, I have a four wire alternator, and I'm making my dune buggy street legal. I know the B+ goes to the battery, but not sure the D-, D+, DF goes. I don't have a regulator, will I need one, if so, what is the part number? Also I have a volt meter gauge that I would like to use. Can I hook it up on the alternator? Thanks

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Tue Jun 05, 2012 4:20 am

That would be an externally regulated alternator like pictured above top. You will need the proper VR to go with it. It has been suggested that if you have a Motorola alternator, you stick with a Motorola VR. And Bosch for Bosch.

The best place to connect a voltage meter is at the battery. This will give you the best representation of the state of charge of the battery when the alternator is not spinning... and how well the alternator is charging the battery while it IS spinning.

Tue Jun 05, 2012 8:30 am

you have speedy jims page..

then you have the oem drawings above. tech, wiring ,type +year

so ,if say, you have a bug or bus
like 60s or had no wiring at all. for what ever reasons.

just use Jims or copy the car year, that your style mimics. (see tech above)

if using , a custom setup, use the instructions that came with...

there are vast posts this forum.
search "alternator conversion"

my favorite is the one that some guy took stock under seat
reg, and stripped it and made it a junction box , crossover.
genious
or the guys that hide electronic reg, in a antique relay OG box,
looks stock , not.
im running a GEN with new updated reg by bosch, has better regulation.
a bosch 30019 ($26 bucks too)

thanks ashman for posting the real functions of D+
it does have 2.

Tue Jun 05, 2012 8:46 am

erich777 wrote: I wired my Bosh Alternator like the example in Speedy Jim, but I dont think I did something right.

Its a 60 with a 1776, and there was NO original wiring for me to go on.

Where does D+ go exactly???
I have it wired up to the ON of my ignition switch, but this causes the car to NOT shut off. (once running, power keeps coming up from D+ and back down through the ignition switch to the coil.)

Do I need to put a diode in to prevent this?

you running electronic ignition. ? you need to post this with full car spec.
my MSD comes with the diode that prevents the idiot lamp from
activating my electonic ignition. RUN ON.

or make a drawing of your custom engine electrics..
and post that.
all these issues are easy to iron out, given full dis-closer....

do you need my MSD chapters on this topic, it on their web site.
why and how to cure.
you need to have the idiot lamp go dead , key off ,like stock, is it?

the idiot lamp can use 3 modes
1- IDIOT (gen dead) NO LEDS allowed, or you are nuts, (well i can do it but need a shunt resistor but neat LEDs are no good)
2: voltage regulation sense point
3: excitation current. (you key on and reg wakes up)

seems just a lamp, huh, but that is not true.

if you had a real schematic for each regulator , all this would be childs play
but we dont. I only have few vw. (and 100s for all cars, showing me the trends)