Wiring for dummies

[thebeast61]

OK i am converting my 61 GMC with 305 from generator to alternator and need help. I have been researching and reading but i just dont understand the writeups because i am an idiot when it comes to electrical work. I dont understand schematics and need a very dumbed down explanation with pictures.
The problem is that most of the descriptions give the wires names or colors and the colors dont match mine and telling me what the wire is for dosent help either cause i dont know which is which.
I would really appreciate if someone could post pictures of the actual generator and voltage regulator wires before and after the conversion.
I am using http://www.classicparts.com/1960-62-...ctinfo/52-895/
I am using a 12si alternator
Thanks guys.

[64fleetside]

I'd use the one wire version Delco, run one 10ga wire to battery, done.

ETA-is the 12SI the smaller alt used on later engines like the LS?

I work a parts store & sell a one wire alt for about $50, its real popular w/hot rodders & tractor/equipment guys.

[61_FL_Apache]

Originally Posted by 64fleetside

I'd use the one wire version Delco, run one 10ga wire to battery, done.

2nd that.

[awbrown]

And I will third that , I just did it to mine last week ,one wire and a voltmeter and you are good to go ... with some one wire setups the engine has to reach 2500rpm before it will kick on , so dont be alarmed if you dont see it charging at first ....

[thebeast61]

but with the one wire i cant hook in the idiot light can i?

[64fleetside]

prolly no on the idiot lite, if you gotta have it then just use the reg Delco, hook the white smaller wire to the wire that went to field on the OE regulator, that should excite the field of the alt & still make the GEN telltale lite function IIRC.

[fixit-p]

If you just want a battery charger go with the 1 wire otherwise they are junk. The 12SI in the 3 wire configuration is more efficient than any 1 wire hands down. Here is a good comparison between the 2 http://madelectrical.com/electricalt...hreewire.shtml
Search the electrical section there are plenty of threads which have walked the OP thought the wiring.
Here is a very simple diagram of a 12SI wiring.

[64fleetside]

I've installed dozens of those "junk" one wire alternators, they work fine. I've done it w/3 wire alts too(wayyy back before one wires were available), both ways work-the one wire is easier to install for a novice.

[thebeast61]

i really prefer the three wire from all the reading i have done. I have seen those diagrams but my problem is i have more wires than are shown on the digram. 2 to the generator and 4 to the regulator plus another small one to the regulator with an inline fuse. I dont know what to do with all these wires. I dont know which one is the field wire or where they go. That is why i was hoping for a picture.

[awbrown]

I am going to do this to my truck this weekend , I will let you know how it turns out .......And dont wire your idiot light wire to the ignition , wire it to the acc or you may not be able to shut it off due to backfeeding throught the wire....

[fixit-p]

Do you have a gen light or ammeter dash? I wouldn't recommend connecting the field wire to the ACC circuit (if you have one) it needs to be connected to the ignition circuit in series with a light, resistor or both in parallel. It is normal for the alt to have full voltage present at the #1 terminal (feedback), if you have run on there will be a reason why as well as a solution.

[thebeast61]

Originally Posted by awbrown

I am going to do this to my truck this weekend , I will let you know how it turns out .......And dont wire your idiot light wire to the ignition , wire it to the acc or you may not be able to shut it off due to backfeeding throught the wire....

oh good. take pictures please.


I do have a light and an ammeter gauge. I guess i dont really have to have the light if i have the gauge though. any thoughts on this?

[fixit-p]

Originally Posted by joedoh

lets not forget that a bad indicator lamp prevents the alternator from charging on the 3 wire setups. some guys like the light though, tells them when they throw the fan belt before the coolant gauge spikes.

True but if the light doesn't come on once you turn the key on , you already know there is a problem and if the resistor is wired parallel to the bulb it adds redundancy and will still work if the bulb burns out.

Originally Posted by thebeast61

I do have a light and an ammeter gauge. I guess i dont really have to have the light if i have the gauge though. any thoughts on this?

You don't need both but you do need resistance on the field wire and that can come from the bulb, resistor or both as mentioned earlier. The conversion is very simple I don't have pics but here are the steps you need to perform.

1. Eliminate regulator replacing it with a junction stud.
2. Connect all wires removed from the Batt terminal on the regulator except for the wire which goes to the gen light EDIT>> Correction the gen light tell tale wire should be on the gen terminal (my bad) to the junction stud created in step 1.
3. On the alternator connect terminal # 1 to the remaining wire that comes from the bulb (field circuit).
4. Connect the 12 ga. brown wire from the gen terminal on the old regulator (1 end to the junction created in step 1 and the other end on the batt terminal of the alternator.
5. Run a wire from the # 2 terminal on the alternator to the batt terminal of the alt. or even better would be to run it to the junction created in step 1.

[joedoh]

lets not forget that a bad indicator lamp prevents the alternator from charging on the 3 wire setups. some guys like the light though, tells them when they throw the fan belt before the coolant gauge spikes.

[joedoh]

maybe, but DC lights tend to burn out when you turn them OFF, in the cooling stage. So you could drive for literally miles with an unknown problem after the dash light at startup reassures you everything is fine. A resistor is a workaround, but then the idiot light just alerts you when the bulb needs replaced, by not turning on.

run an ammeter, or a voltmeter, and leave the idiot lights to people who need them. pun intended, offense not intended

[awbrown]

Well here is what I had , I swapped this alt. on because the other was for a 6cyl. or something and the pulley just didnt line up.. This one is not perfect , but it is drivable .. So in a rush I simply made it a one wire setup.. Then I cut the connector off for the old alt. and connected the red wire to terminal 2 and the blue to terminal 1... then off to the other side and .. The top red wire that connects to the horn relay is from the battery , the brown wire coming out of the harness at the bottom of the picture is from the harness going to the dash (the wire to the idiot light/switch ) it gets connected to the blue wire that was disconnected from the old regulator .. the red wire that we hooked up at the alt. gets hooked to the junction/horn relay after being disconnected from the regulator .. And cut the red wire going into the regulator that hooks to the junction ..

[thebeast61]

ok thanks for the help. I should be able to get it from that. I dont know why but anything electrical is like greek to me. It just is very hard for me to grasp.
Thanks to everyone that replied.

[fixit-p]

Originally Posted by joedoh

maybe, but DC lights tend to burn out when you turn them OFF, in the cooling stage. So you could drive for literally miles with an unknown problem after the dash light at startup reassures you everything is fine. A resistor is a workaround, but then the idiot light just alerts you when the bulb needs replaced, by not turning on.

No offense taken here but once the alternators field is excited it will sustain itself so you could remove the bulb after the engine is running and the alternator will still work the resistor is not a workaround but rather a part of the circuit

Originally Posted by awbrown

Well here is what I had , I swapped this alt. on because the other was for a 6cyl. or something and the pulley just didnt line up.. This one is not perfect , but it is drivable .. So in a rush I simply made it a one wire setup. The top red wire that connects to the horn relay is from the battery , the brown wire coming out of the harness at the bottom of the picture is from the harness going to the dash (the wire to the idiot light/switch ) it gets connected to the blue wire that was disconnected from the old regulator .. the red wire that we hooked up at the alt. gets hooked to the junction/horn relay after being disconnected from the regulator .. And cut the red wire going into the regulator that hooks to the junction ..

It is still a 3 wire unless you change the regulator.
thebeast61, from looking at the third picture it looks like he went from external alt to internal alt and you are going from generator to alternator apples to oranges, if you get confused post back some pictures of your own. I see the thread is in the electrical section now IMO that where it belongs.

[VetteVet]

The absolute easiest way to convert to an internally regulated SI alternator is to find the generator tel light wire ( it should be a brown wire from the front firewall connector ) and connect it to the no. 1 terminal on the alternator and then run a short wire from no.2 terminal on the alternator to the large terminal on the back of the alternator. Then run the large feed wire on the back of the alternator to the battery or horn relay hot post.

Here is a picture, the brown wire on the alternator is the gen light and the red wire goes to the back of the alternator. The blue wire comes off the same large terminal and is spliced into a red wire to reach the horn relay with a feed wire to the battery positive post.
Fixit-P has the best solution, but if you're electrically challenged you can go the simple way.
The gen light has to work as the alternator needs to see some resistance to excite the alternator field, it also prevents feed back to the ignition circuit which would cause the engine to keep running. You can't connect to the accessory circuit because the trucks didn't have one until 1968.

[thebeast61]

Ill post pictures as soon as i can and show you what i got and see what yall think

[awbrown]

I was intrigued , so I went out to my 63 and pulled the ignition switch out and it is a 5 pin switch , of those pins one is ground , one is d-r or sol for the starter, one is ign. , one is batt , and the last one has a brown wire going to it , you wouldnt guess what that terminal was .............

[thebeast61]

ok this is what i have. I already removed the regulator and gen. I hope you can tell me what to do with each one of these wires. Notice that wire going down by itself with the inline fuse too. not sure whre it goes. its all taped up in the harness.

[IMG][/IMG]

[awbrown]

You will have to clean up the wires so we can see what color they are .. It looks like it had a generator by the lugs that were left ,no problem .. The wires dont have to travel accoss the front and then back , only the wire that runs the fuse box.. If the wire for the fuse box runs all the way around the front you would be better to wire it like a mid 70's truck and run your wire from the fuse box off the starter lug that the battery cable goes to ,and also hook your alt. to the same terminal ,it will shorten that wire up instead of running all the way around the front of the truck ...like in post # 7 the junction where all the wires meet will be at the starter.....

[VetteVet]

Here''s a pic of the generator regulator and the wires match your picture.

The red wire is the Bat wire and the brown wire with the black is the Gen wire and the blue wire is the field wire. I can't say what the fused wire is.



One thing to consider is that you most probably have an internal shunt ammeter.
What this means is that all the battery and the generator wires run through it. You will have to take this into account when you are rewiring the dash and the gauges. Check the wires to the ammeter and see if they are larger than the other wires in the dash. If they are then the wiring will be like this.

[fixit-p]

That fused wire if it goes into the harness maybe the ammeter lead, this is the only schematic I have for a 60-61 and it implies that the ammeter is an external shunt but the 3 amp fuse is shown to be at the starter side. Like Vettevet said the wires at the ammeter would tell if it is external or internal shunt.


Earlier I stated the wire from the gen lamp was at the batt terminal on the regulator, its actually at the gen terminal and maybe black in color this wire gets connected to the blue wire for the field circuit. Brown and red are connected together at the buss.