Help with 12 volt wiring on ford 640

[jaotguy]

# 2 pin should be disconnected from the battery when the ignition is off .... just in case .

if the regulator fails while connected , it can draw down the battery ... but you can take the chance if you feel like it ( still pretty safe )


still a very good diagram of most wirings of a GM alternator :thumbsup:

 

[8N Ren]

I can't take credit for it, I grabbed it off the web.
My understanding was that if you put in the marker light or a diode that stops the battery draw and you leave everything connected.
Light is off when the engine is cut, at start up the light is on and after a second or two light goes out, if something is messed up then the light will stay on.

 

[jaotguy]

almost correct .. the sense wire is always "live" in that picture ... and should not draw any power at all ( usually) ... but if the circuit inside fails ( you boosted someone wrong , connected the battery wrong , etc ) it will start drawing the battery down and possibly cook the wiring harness if the draw is high enough ....

the "excite" wire and indicator light should only be connected to power when the engine is running .... it feeds power to one side of the internal regulator to power the armature so it will start charging .... ( so that makes it 12v from battery to light to armature to ground, a complete circuit and the light is ON ) .... once the alternators starts charging , there is over 12v on the armature by itself , (there is now 12V from the battery to light to armature to 12V , no ground so the light goes out) .... if you leave the excite circuit connected to the battery all the time , the light will be on all the time ... and a dead battery the next day.


the reason they use a light ( and shows if the alt is working ) / resistor , is because without it , the 12V from the exciter circuit is often enough to backfeed the ignition and keep the vehicle running ( even when you turn the key OFF ) ... the light limits the power so it can't do it .

 

[8N Ren]

Well put J, sometimes me fingers and me mind don't do what I want lol.

 

[Soundguy]

while that wire setup WILL work. it does leave the alt in a tricky situation if the wire from the key opens, as the sense circuit is unloaded.

it is safer to loop #2 to the charge stud, then run #1 thru the 194 lamp to the coil side of the key switch.

charge wire from the alt to one side of the ammeter, other side of ammeter to battery hot.

wire powering lamps and key switch should come off same side of ammeter as the alt charge wire.

this preserves the net charge / discharge function of a center 0 reading ammeter that a ford 00 series would have.

a large RED goes from the big BATT post on the alt to one side of your ammeter , out the other side and over to any large POS connection on the battery ( you can skip the ammeter and go directly to the battery , but the gauge will not read )

you need a wire ( any color about 16 gauge ) from the I terminal on the ignition switch to the #2 pin on the alt ...

you can then just put a small light bulb (with a connector and 2 wires ) between the #1 and #2 pins .. the light should come on when you turn
the key to ON .... and go out when the engine starts , if it doesn't , the alt is not putting anything out .
or run a wire from the I on the switch up to a light on the dash somewhere and back to the #1 on the alt ...

the black yellow used to be the wire going from the original alt output to the ammeter gauge ( and RED out the other side, back to the big POS wire on the starter ) It should have been about #8 or #10 wire ... but it looks like you'll have to trace to see if its still connected , or has been bypassed during the original conversion .... ( or leave it bypassed )


one word of caution ... if the smaller pins are not labeled 1 and 2 and have R an F instead , you have an alt that needs an additional external regulator to work

 

[jaotguy]

agreed , both will work ... the jumper from the BATT on the alt to #2 pin will work just as well (and avoid a possible wiring loom fire)

more than 1 way to skin a C*t ...

many other setups will work just as well ... unfortunately, we don't know what was done to "upgrade" the charging system ( what was bypassed, cut out , rewired , etc ) by the other owner ....

try to keep things a neat as possible ... use different color wires for each circuit ..... draw out what you have done ( and what you have traced ) and keep copies for later ....

 

[Soundguy]

# 2 pin should be disconnected from the battery when the ignition is off .... just in case .

if the regulator fails while connected , it can draw down the battery ... but you can take the chance if you feel like it ( still pretty safe )


still a very good diagram of most wirings of a GM alternator :thumbsup:

there is no reason to take #2 off with ignition off. if the alt is bad.. replace it.

 

[Soundguy]

that's why on a tractor with a simple wire harness like this. it is adviseable to just build from scratch. should take 10 minutes with a tool and terminal kit and some wire looming.

agreed , both will work ... the jumper from the BATT on the alt to #2 pin will work just as well (and avoid a possible wiring loom fire)

more than 1 way to skin a C*t ...

many other setups will work just as well ... unfortunately, we don't know what was done to "upgrade" the charging system ( what was bypassed, cut out , rewired , etc ) by the other owner ....

try to keep things a neat as possible ... use different color wires for each circuit ..... draw out what you have done ( and what you have traced ) and keep copies for later ....