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Author Topic: oem alternator wiring  (Read 248 times)

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mdidomenico

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oem alternator wiring
« on: June 13, 2022, 01:58:34 PM »

i'm working on getting my engine all rewired.  i've pushed through the forum threads on alternator wiring, but either i don't understand what i'm reading or i don't understand what two of the screws on the back of alternator are for or both.  so a picture is worth a thousand words.  attached is the back of my alternator.  i can identify the B+ (goes to battery), the AC tap (goes to tachometer).  but there are three other screws, one just above the AC tap and 2 about 12o'clock and 2 about 3o'clock.  one of the screws at 12 and 3 clearly hold the case together (same head pattern as the two in the center), but what are the other two for at 12 and 3.  i think ones a ground and the others a sense wire, but i'd rather not guess

assuming one of the bolts is for a negative wire back to the batteries what gauge is that supposed to be.  clearly it's not the #2 i'm using for the B+
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1989 Cat34 #856, original m-25xp

KWKloeber

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Re: oem alternator wiring
« Reply #1 on: June 13, 2022, 09:28:08 PM »

MD

It *appears* that you have an 8EM2017KA (51 amp). 


12:00 is the V Sense terminal.
3:00 is the Field Excite terminal.
4:30 is the GND terminal.

There is really no reason to run the GND wire back to the bttys.  You can run it to the NEG btty cable, which OEM is on the tranny bell housing.  If so, that cable lug should be moved from there to the outside starter bolt.

For a 51a alt I would use a #6 or #4 gauge. 
A #8 is allowable, But You Never Get A Second Chance To Overkill It The First Time.


Y’all - check your cable lugs; don't assume OEM ones are good.  This was a CTY factory crimp on a C355!!

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Twenty years from now you'll be more disappointed by the things you didn't do, than by the ones you did.
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Explore.  Dream.  Discover.   -Mark Twain

mdidomenico

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Re: oem alternator wiring
« Reply #2 on: June 14, 2022, 09:10:21 AM »

12:00 is the V Sense terminal.
3:00 is the Field Excite terminal.
4:30 is the GND terminal.
There is really no reason to run the GND wire back to the bttys.  You can run it to the NEG btty cable, which OEM is on the tranny bell housing.  If so, that cable lug should be moved from there to the outside starter bolt.
For a 51a alt I would use a #6 or #4 gauge. 
A #8 is allowable, But You Never Get A Second Chance To Overkill It The First Time.
Y’all - check your cable lugs; don't assume OEM ones are good.  This was a CTY factory crimp on a C355!!

as for check the lugs, it's all new using an ftz crimper, so if its broke, it's my fault :)

for the B+ i'm using 2awg from the batteries directly to the alt.  if i understand what you're saying, the negative post is right next to the AC tap bolt and it should be min 8awg.  i can use 2awg for the ground, but i'm afraid the power lugs i have are going to be too large for that bolt.  its not the same size as the B+ bolt

the field excite wire i'm taping off the ignition/fuel pump wire from the panel, 12awg.

where does the vsense connect to?

i'm planning to run the bell house ground and some other negative wires to a busbar in the engine bay and then 2awg back to the batteries

and just to double check the starter doesn't have a separate ground it's ground comes from the engine ground right?  it just has the positive lug and the solenoid positive wire.  is there a reason to use the starter bolt over the engine/tranny bolts as a ground

i think i got everything else hooked up right though, so we'll see, maybe this weekend, if it actually starts up again... :)

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Stu Jackson

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Re: oem alternator wiring
« Reply #3 on: June 14, 2022, 10:42:05 AM »

When I installed my new alternator, I drew wiring diagrams of what was there on my old one, too.

Alternator Regulator Wiring Diagrams - all three http://c34.org/bbs/index.php/topic,4548.0.html
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mdidomenico

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Re: oem alternator wiring
« Reply #4 on: June 14, 2022, 12:00:14 PM »

When I installed my new alternator, I drew wiring diagrams of what was there on my old one, too.

yeah, that probably would have helped.  i got 98% of the system rewired.  the real crux was just not knowing which post was which in the alternator.  one cause i didn't know the model number and two because the yard painted my engine.  they taped off a lot of the decals, but i guess the alt was a step too much.
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1989 Cat34 #856, original m-25xp

Stu Jackson

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Re: oem alternator wiring
« Reply #5 on: June 14, 2022, 12:32:15 PM »

When I installed my new alternator, I drew wiring diagrams of what was there on my old one, too.

yeah, that probably would have helped.  i got 98% of the system rewired.  the real crux was just not knowing which post was which in the alternator.  one cause i didn't know the model number and two because the yard painted my engine.  they taped off a lot of the decals, but i guess the alt was a step too much.

I understand, but I drew the diagram which shows the internal regulator on the back of the alternator which should allow you to figure out what posts are which.
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KWKloeber

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Re: oem alternator wiring
« Reply #6 on: June 14, 2022, 12:39:37 PM »

MD

On that alt the model no is on a sticker on the back. I have a pic of one with an “intact” sticker.

Most have a sticker with the model no of the REGULATOR not the alt model number.  (The alt model is stamped into the side of the case at the forward end.)
Yours MIGHT ALSO have the model number stamped in, behind the belt, on the side part of the case near the hinge point.

Doesn’t matter though, it’s a 8EM2017KA.

I’m on the road and can answer your other Q?s later.

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KWKloeber

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Re: oem alternator wiring
« Reply #7 on: June 14, 2022, 12:43:37 PM »


I understand, but I drew the diagram which shows the internal regulator on the back of the alternator which should allow you to figure out what posts are which.


Stu

He has a different alt than the 2094K series and has different terminal locations and a V sense which yours doesn’t.
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Twenty years from now you'll be more disappointed by the things you didn't do, than by the ones you did.
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Explore.  Dream.  Discover.   -Mark Twain

KWKloeber

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Re: oem alternator wiring
« Reply #8 on: June 14, 2022, 03:57:26 PM »

12:00 is the V Sense terminal.
3:00 is the Field Excite terminal.
4:30 is the GND terminal.
There is really no reason to run the GND wire back to the bttys.  You can run it to the NEG btty cable, which OEM is on the tranny bell housing.  If so, that cable lug should be moved from there to the outside starter bolt.
For a 51a alt I would use a #6 or #4 gauge. 
A #8 is allowable, But You Never Get A Second Chance To Overkill It The First Time.
Y’all - check your cable lugs; don't assume OEM ones are good.  This was a CTY factory crimp on a C355!!

as for check the lugs, it's all new using an ftz crimper, so if its broke, it's my fault :)

for the B+ i'm using 2awg from the batteries directly to the alt.  if i understand what you're saying, the negative post is right next to the AC tap bolt and it should be min 8awg.  i can use 2awg for the ground, but i'm afraid the power lugs i have are going to be too large for that bolt.  its not the same size as the B+ bolt

the field excite wire i'm taping off the ignition/fuel pump wire from the panel, 12awg.

where does the vsense connect to?

i'm planning to run the bell house ground and some other negative wires to a busbar in the engine bay and then 2awg back to the batteries

and just to double check the starter doesn't have a separate ground it's ground comes from the engine ground right?  it just has the positive lug and the solenoid positive wire.  is there a reason to use the starter bolt over the engine/tranny bolts as a ground

i think i got everything else hooked up right though, so we'll see, maybe this weekend, if it actually starts up again... :)


Lugs should go down to #10 hole. I believe that’s the size of the GND.  At least I buy them down to that size.
The AO post should be 1/4”.

The alt will put out only 50a absolute PEAK, and your Alt HAS voltage sense (not typical)!! so why use 2 awg???  Crazy cookoo but YBYC.

Note that the previous diagram I posted was for a customer who didn't want to sense btty V.

I did a diagram of two different ways to hook up a negative buss in the engine compartment.
https://c34.org/bbs/index.php/topic,11183.msg88980.html#msg88980

Let me suggest, and take this is the spirit it's meant, if one rips out an Alt w/out making a schematic, doesn't know why to run a NEG to the heavy-load starter, and doesn't know what V sense does - it might behoove one to get a professional to help them rewire.  It isn't something to be done without knowing the most basic items about the charging system. I'd hate to screw that up!!



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Twenty years from now you'll be more disappointed by the things you didn't do, than by the ones you did.
So throw off the bowlines.  Sail away from the safe harbor.  Catch the tradewinds in your sails.
Explore.  Dream.  Discover.   -Mark Twain

Stu Jackson

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Re: oem alternator wiring
« Reply #9 on: June 14, 2022, 06:34:12 PM »


Stu

He has a different alt than the 2094K series and has different terminal locations and a V sense which yours doesn’t.

I see now, thanks for posting that diagram.
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mdidomenico

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Re: oem alternator wiring
« Reply #10 on: June 15, 2022, 07:29:12 AM »

Lugs should go down to #10 hole. I believe that’s the size of the GND.  At least I buy them down to that size.
The AO post should be 1/4”.

ah, that's the part i was missing.  i totally missed that the lugs will go down to a #10 post.  the B+ is definitely 1/4" i checked the lug fit last weekend

The alt will put out only 50a absolute PEAK, and your Alt HAS voltage sense (not typical)!! so why use 2 awg???  Crazy cookoo but YBYC.

mostly its just because it's what i have on hand and i don't have a tool that will crimp 8awg wire.  so the closet i could get to your suggestion would be 6awg (w/ftz crimper), but i already have 2awg, so if it doesn't hurt why not

I did a diagram of two different ways to hook up a negative buss in the engine compartment.
https://c34.org/bbs/index.php/topic,11183.msg88980.html#msg88980
Let me suggest, and take this is the spirit it's meant, if one rips out an Alt w/out making a schematic, doesn't know why to run a NEG to the heavy-load starter, and doesn't know what V sense does - it might behoove one to get a professional to help them rewire.  It isn't something to be done without knowing the most basic items about the charging system. I'd hate to screw that up!!

it's not that i don't understand it's that i don't understand what i'm looking at because things aren't labelled (and weren't when i pulled the wiring out and i hadn't documented what i pulled out as well as i thought i had)

but these two sets of diagrams (alt and neg wiring) make it all clear now what i'm looking at.  and since i'm re-wiring things i'm making (clearer) diagrams as i go, but it's not much different then what CTY originally built
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KWKloeber

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Re: oem alternator wiring
« Reply #11 on: June 15, 2022, 08:27:22 AM »

@MD

Gotcha.
So are you re-cabling the bank to the starter as well with #2?

V loss wise, and ampacity wise, I’d use #6 for the alternator neg to the buss/or/to the starter just for ease of doing it. It’s only 18” IIRC for that cable.   I know what you mean about #8 - I have a dedicated hex crimper for that for starter lugs and two die crimpers I can use for power lugs.
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Twenty years from now you'll be more disappointed by the things you didn't do, than by the ones you did.
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Explore.  Dream.  Discover.   -Mark Twain

mdidomenico

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Re: oem alternator wiring
« Reply #12 on: June 15, 2022, 08:56:44 AM »

So are you re-cabling the bank to the starter as well with #2?
V loss wise, and ampacity wise, I’d use #6 for the alternator neg to the buss/or/to the starter just for ease of doing it. It’s only 18” IIRC for that cable.   I know what you mean about #8 - I have a dedicated hex crimper for that for starter lugs and two die crimpers I can use for power lugs.

correct, alt and start post go back to the battery via separate wires protected (at batt) by ANL fuses in bluesea holders.  OEM was 4awg, i upsized to 2awg

i'm putting a bluesea busbar in the engine bay which will be the negs for start, alt, fuel pump, fuel tank sender, eng blower, and eng panel, which will go back to the batt with 2awg

just to simplify the parts (and spares), everything is basically either 2awg or 10/12awg wire

i've basically been following the CD panel wiring https://www.catalinadirect.com/images/features/Z4644%20Wiring%20Diagram.pdf and what i've been able to pickup as recommendations from you, Stu, and Rod
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