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View Full Version : how to wire gm alt for 1 wire set up?



jasonsnova
03-26-2010, 04:33 PM
ok guys building new engine (6.0 with ls3 heads,carb'd) for my 71 nova , tonight i got my pace/gm corvette accessory drive all mounted up, question is how do i wire the altenator? the plug that came with the alt has four wires, in the pic below the one furthest to the left is a dummy, but i have no idea what to with the other ones, i know on oem/fuel inj set up the computer controls the voltage...i have no compter(carb ) so....how do i go about making this work ....and work so that it wont burn up in 5k miles! lol

Gitter Dun
03-26-2010, 06:53 PM
A one wire alternator has an internal regulator and for this reason only one wire is needed. Most common one wire alternators are the Delco model SI and you can find one of those any where. Since you have discovered the dummy the other 3 should be Bat, Field, and sensing. I dont know what alternator you are using, I picked mine up from Jegs. All I had to do was run a 10 ga wire from the batt post at the back of the alternator to the battery post on the starter

MonzaRacer
03-26-2010, 09:52 PM
Depending on the plug P terminal is not used, the S terminal can be either looped to battery post or ran to battery to let regulator sense the system charge. the F terminal is unused and with stock wiring from "idiot" light with bulb installed and receiving fused 12 volts key on run through the light then to the L terminal.
Basically you do need 2 wires and if you run a large stereo the S terminal wire going to battery helps alt sense lower voltage as its being drawn from system. or you can just loop it to the alternator battery post.
Ask if you have anymore questions.
Lee Abel
AFTERMARKET PERFORMANCE

astroracer
03-27-2010, 02:21 AM
Check out this site. Lots of good info.
http://madelectrical.com/
Mark

jasonsnova
03-27-2010, 05:33 AM
i know years ago i used a old style gm internal reg and all i had to do was loop 1 of the 2 plugs on the back to the bat terminal on the alt, but this one looks a bit different it is gm part # 25888970 if that helps , it is whats used on 05 corvettes.... heres a few close ups
so if what monzaracer is saying is correct all i have to do is run the "S" wire to the battery and i should be good right? from what i gather i could run it to the post on the alt but it will sense voltage better running it to the battery...am i missing anything?
also from what i can see i have a S F & L terminals on the alt, different letters and numbers on the actual plug

mc84_zz4
03-27-2010, 09:21 PM
Here is one that I used when switching mine to the serpentine setup. Of the SFLP in the connector, S is the battery(Big wire), L is the other one needed to turn the alternator into charge mode, otherwise it will not charge (non-1 wire). The other 2 wires are not used.
My guess is if it is internally regulated, the 'S' is all you need, (which also loops to the alt positive terminal)
HTH
http://paceperformance.com/index.asp?PageAction=Custom&ID=650
Probably not very relevant for yours, but here is a shot of the 2 wire common alternator setup, the S looping to the Alternator positive terminal, which also leads to battery (+) (not visible in pic is the Battery + wire, You can ignore the extra ground to the Alt frame)
http://www.motortopia.com/files/12469/album_misc/490138992d44a/132-3224_IMG.jpg

jasonsnova
03-28-2010, 08:26 AM
Here is one that I used when switching mine to the serpentine setup. Of the SFLP in the connector, S is the battery(Big wire), L is the other one needed to turn the alternator into charge mode, otherwise it will not charge (non-1 wire). The other 2 wires are not used.
My guess is if it is internally regulated, the 'S' is all you need, (which also loops to the alt positive terminal)
HTH
http://paceperformance.com/index.asp?PageAction=Custom&ID=650
Probably not very relevant for yours, but here is a shot of the 2 wire common alternator setup, the S looping to the Alternator positive terminal, which also leads to battery (+) (not visible in pic is the Battery + wire, You can ignore the extra ground to the Alt frame)
http://www.motortopia.com/files/12469/album_misc/490138992d44a/132-3224_IMG.jpg

thanks that helps.. but as i have all autometer gauges and no dummy light...so according to the diagram i need a resistor any one know what one or a part #? i did read in a post on ls1tech someone cooked a alt not running a resistor .

jasonsnova
03-28-2010, 11:15 AM
ok just did a quick search on ebay for 470 ohm resistors....turns out they make them in several different wattages... so guess i still need to know what resistor to run...??