Alternator Install Question

1941 - 1945, MB, GPW modifications, sugestions, and ideas, official MWO's and unofficial WWII field mods NO EBAY or COMMERCIAL SALES.
Post Reply
M14
G-Corporal
G-Corporal
Posts: 23
Joined: Wed Oct 12, 2005 12:45 pm
Location: Renton Wash

Alternator Install Question

Post by M14 » Tue Feb 09, 2021 2:37 pm

I'm going to be removing the crude solenoid system on my jeep and installing a new proper wiring harness. The only deviation is I'm using a 3-wire alternator (low amp).
I'm not totally clear on how to properly wire it in using the original type jeep wiring (floor start, ammeter etc). I'd rather not fry anything if I can help it!
Thanks for any insight!
Willys Mb Slat # I08I50


Adam
G-Lieutenant General
G-Lieutenant General
Posts: 4525
Joined: Sun Jul 20, 2003 6:03 pm
Location: Little Meadows PA

Re: Alternator Install Question

Post by Adam » Tue Feb 09, 2021 8:36 pm

Why 3 wire? they were obsolete 20 years ago,
Kinda remember tying both the leads from the small plug together, use a diode and connect it to a switched power source, like the coil. output from the generator just goes through the amp meter like the old setup. just find the wiring info for your genny,, probably an old delco remmy.

Adam

Wolfman
G-Lieutenant General
G-Lieutenant General
Posts: 6872
Joined: Sat Jan 12, 2008 5:25 am
Location: Tipton,In.

Re: Alternator Install Question

Post by Wolfman » Wed Feb 10, 2021 6:44 am

First off, what make alternator are you installing ???
What ever it is, the wire that would normally go on the " Batt" terminal on the voltage regulator, from the amp gauge, would now be connected to the large " Batt" post on the alternator.
Obviously no need for the voltage regulator at all, unless you are going for effect.
Now I am assuming. ( there's that word ).
Delco 3 wire, with an internal voltage regulator, has a flat plug on the edge. What Adam was referring to.
Terminals labeled "1" & "2".
Terminal 2 is a system voltage sensing connection. Feeds system voltage information to the internal regulator so it can regulate alternator output voltage and can be connected to any battery B+ source. Does not have to be switched. GM, on their grain trucks, used to just loop this wire over and connect it to the big battery post on the back of the alternator. Very simple.
The #1 terminal is to excite the alternator on start up. It does need to be switched.
Once the engine is running and the alternator charging, this #1 wire could be disconnected and the alternator would continue to charge until shut down.
The need for the diode Adam referred to is, if the #1 wire is connected to the IGN. post on the switched side of the coil without a diode, power from the charging alternator would feed back to the coil. You would not be able to shut the engine off just by turning the ign. switch off.
Option one to using a diode. GM connected the #1 wire to the alt. idiot light on the dash. Before the alternator started charging on start up, current flowed through the idiot light to the alternator, making the light come on, and there was enough current to make the alternator "Kick In". Once the alternator was charging, both idiot light wires were at B+ potential. No current flow and the light goes out. When the ignition was turned off and the engine stopped, the light bulb had enough resistance to prevent enough current from back flowing to the ignition to keep the engine running.
Option 2. Use an ignition switch with an "accessory" post. Connect the wire from terminal #1 to this post. Internally in the ign. switch, Accessory and Ignition are not connected together in the off position. When the switch is turned off, the back flowing current from the alt. #1 terminal doesn't have any place to go. You have shut down.
Hope we are dealing with a GM 3 wire after all this.
Adam's One wire suggestion is a good one. :D
Mike Wolford
CJ-2A
VEP GPW
Comm./Inst. SEL
AOPA ( 50 yrs)
EAA ( 49 yrs)
4th Inf. Div. - 5th Inf. Div. - 2nd Armor Div. - CIB


Post Reply

Return to “MB GPW Modifications”

Who is online

Users browsing this forum: No registered users and 4 guests