fitting later -75 Motorla alternator to swb voltage regulator

[turre]

Hello!

Can someone please help me with this! Im building a 912 with 2.8 Type 4. With Porsche 911 5 blade fan.

How do i connect the Motorola alternator to work with this setup. The voltage regulator that i have is standard for swb cars. What wires do i need and where do i connect them. // Oskar

this is the backside of my alternator.

[Trackrash]

This thread shows the wiring. The black and blue go to the regulator. I am guessing you will need one of the newer 911 regulators available from our host. The large red wire goes to the starter which is the connection to the battery. Brown is ground. On 911s there is another ground to the engine case.
I imagine you will be making your own custom harness.
Marchal Alternator Trouble--Wiring or Ground?

[turre]

Thank you so much! Yes im going to make a custom harness. I work as an Electrician so i have plenty of stuff to work with.
Can someone confirm that a need the later model 911 regulator?

What kind of square/mm should the diffrent cables be? 1,5mm and to starter 4-6mm? // Oskar

[Trackrash]

Just make sure the regulator is compatible with the Motorola alternator.

As far as the wire size goes, here is the SC diagram showing the wire size that they used. http://www.pelicanparts.com/911/911_parts/Electrical/911_electrical_82SC_Part1-1.jpg

[clarkd]

Do you have the red isolation plate shown on the alt in the link above?

[Trackrash]

Here is what mine looked like when I first removed it from my '71.

[Trackrash]

Here is a better shot of my '71's alternator. In the bottom picture is an alternator out of a '78 SC, it does not have the red block. Maybe an expert can chime in.


For comparison from a '78.

[clarkd]

No expert, but the 55 amp SEV 71223702 model alt does not have field diodes. The bias of the two diodes in the isolation plate prevent your battery from discharging through the alt when the car is not running.

[turre]

Hello again back to this, went to the garage to hassle with this and of course went in to a bit of problem. I dont have the Red Isolation plate, so therefore i dont have a B+ to connect to battery. Can i make this somehow without the red plate? i have a bettery killswitch in the car so i dont need to worry about the battery getting discharges that way. You can se a picture on the top of the thread of my alternator and were to connect stuff. // Oskar

[turre]

Still wondering if i need the red diode plate! really need to know to get my engine back in the car!

[30westrob]

You do not need the red diode plate, just use the correct voltage regulator for the alternator you are using. Rob

[Jack Stands]

Though I'd always heard that you should use the same brand voltage regulator as the alternator, I always wondered why? The wiring on the external regulator is all the same, and the electrons don't care where they came from!

[timmy2]

Regulators are rated for the output of the alternator they are designed for. Old regulators may burn up with newer higher output alternators.

[turre]

Okey!
Thank you so much! Just one last question now! Since i dont have the red diode plate i have nothing to connect the Red battery cable to. My guess is to connect it with the D+/61 is that correct? //Oskar

[30westrob]

No Oscar. The heavy gauge red battery wire goes to B+ post on the alt. If it is not marked it will be the large post that is insulated as it goes through the case and connects to the power diode plate in the alt. Some Alts. have 2 B+ posts, you cane use either one. Rob

[timmy2]

Photobucket is holding you picture hostage, so I/we can't see the photo of your new alternator.
Post one using Pelican from your photo file and we could give you better directions.
You may be able to see it, but all I see is you need to update your photo bucket account!

[turre]

Okey! cant see another B+ on the alternator.. Maby i can hook the alternator to a drill machine and use a mulitmeter to measure were B+ is?

Here is the picture that you guys could not see anymore.

[turre]

I hate to be greedy... But i really need to know

[timmy2]

Looking at your photo, and all other photos of the same part number alternator, as well as some schematics of that type of alternator, leads me to believe....

You do need the missing red piece, as it has a built in diode bridge connector piece for the two diodes tops that are barely visible in your photo. (Between the studs in the recessed parts.)
The red piece is the Battery positive connection piece?

Based on the schematics in this thread.
Bosch/Motorola voltage regulator compatibility

[turre]

Yes! The red plate gets me B+ and i dont have that plate... This sucks. Hate to buy stuff second hand and its all trouble and missing pieces... Cant find anywhere to buy that plate either.. Guess i will have to buy another alternator