Alternator Not Charging *FIXED

[1967AceStroker]

Well I've tried all I can think of to make it work, but no luck so now I need your help. I did a search first and couldn't answer my own questions.

The truck is '67, but the parts cab and ALL wiring used is a '71 F250 Camper Special. I don't know if anything worked when I got it cause it didn't run. Now that I've got to the point of it running with the new motor I've discovered that the alternator isn't charging. I tested it running and off with my multimeter, so I'm sure it wasn't charging. I had a new factory replacement alternator on it at first, and it didn't charge. I had it tested and it was good. So I figured if I was gonna mess with the wiring I'll just do a 3G swap, so I did. I got a 135amp alt. for a 2000 v6 Mustang. Went to the junkyard and got a factory harness from a mustang. Everything went in good and I installed it using the diagram pictured below. But it's still not charging. I had the 3G tested also, and it was good. I don't get anything on the gauge in the truck either.


So I looked at some wiring diagrams on here to check everything. I noticed that there are no '71 wiring diagrams. I can follow the "70 diagram, but the '72 is a little too fancy for me. And best I can figure out is that the light green w/ red wire from the alt. needs to be hooked into the side of the plug with the light green w/ red wire. I guess that is the wire that tells the alt. to charge. I've looked through all the wiring and nothing seems to be hacked up, or missing. I even tried swapping the gauge from another cluster I had. So I don't know if it's something in the system is wrong and not allowing the alt. to know there is a load and to charge. Pictured below is the plug on the truck I have the light green w/ red alt wire plugged to(yellow wire is for the horn). If that is the right plug then everything should be hooked up correctly and work. I don't know where to go from there. Would adding an aftermarket gauge change anything?


Well I hope I've explained my problem good enough. Any advice, ideas, or info would be much appreciated.

Thanks

[mrollings53]

This is the diagram I used.



That plug you have pictured is not the correct one. The original green/red wire went to the voltage regulator on the radiator support. It's plug is flat and has four or five wires coming out of it.

If you have the amp gauge you'll want to solder in a 560 ohm resistor between the orignal green/red wire and the green/red wire coming from the alt's harness. This will drop the voltage enough to tell the alternator to start charging.

If you have the idiot light you don't need to wire in a resistor, but you can add one like in the diagram as insurance if the bulb burns out.

If you want your amp gauge to work correctly connect anything that draws a load to the fused side of the charge wire. I connected mine right on the mega fuse terminal connection. Then connect the red fused wire to the positve battery post on the starter solenoid and the yellow fused wire to the fused connection where all of the connections that draw a load are.

In my first picture below; on the right is the charge wire coming from the alternator. On the left side of the mega fuse is all the wires that draw power (main power to the fuse block, electric fan). Also there is the other half of the charge wire going to the positive battery side of the starter solenoid, and the yellow fused wire for the amp gauge.

In the second picture you see my charge wire coming from the mega fuse connected to the positive battery terminal as well as the horn lead, the red fused wire for the amp gauge, and some other wire. I haven't connected my positive battery cable yet, but it will go on there also.

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[1967AceStroker]

I know that the green/red wire went to the "I" on the original regulator.
But now it should go to the "I" on the new alternator regulator plug. Right?


If that's the correct wiring, then what could the problem be? Do I need to add a resistor, if so where? My truck has the alt. gauge.

[mrollings53]

So, what did you end up doing to fix the issue? Also did you have any issues with your pulley squealing?

[1967AceStroker]

So, what did you end up doing to fix the issue? Also did you have any issues with your pulley squealing?

Alright, I got it fixed and everything works good now. The pulley did squeak a little so I just tightened the belt a little more and that stopped it.

I figured a bit out about how these 3G alternators and regulators work. The Green wire "I", or "Ignition" needs to go to a switched 12v. What happens is that wire needs to go hot when the key is in the on, or run position. That tells the alternator it's time to start charging. Then the regulator tells it how much to output for charging. And then of coarse with the key off, essentially the alternator turns off.

I found out that I had the Green "I" wire plugged in the right place. But the issue was that that wire wasn't going hot when the key was turned on. So my alternator was never notified to charge. I never could find out why so I ran my own wire.

How I fixed it is I bought some Green 18 gauge wire and found a place in the cab where I could plug into a switch hot. I tested a plug up under the dash that was unused and happened to be a switched hot. I ran my wire from that plug to the Green "I" on the alternator. I was also told to add a diode in the line allowing electricity flow only toward the alternator. A diode is like a one direction valve for electricity. My friend told me the diode will prevent the electricity from flowing back into the cab and causing a possible ignition problem. I'm not sure if you need the diode, but he gave me one and I used it and it works so.

So if your alternator and regulator are good, but not charging, 3G, or old school. You can test that Green "I"/"Ignition" to see if it goes hot when the key is on. And if it's not getting any power, you know what the issue is and can try to find the issue with the original wiring, or run your own wire as I did.

Hopefully I explained all that good enough.

[sargentrs]

Congrats! And thank for posting your solution.