I physically put in the 3-g alternator and did the wiring. I now have no power inside the cab, no radio no dome light no gauges, nothing. If I turn the key to start nothing happens. But if I turn the key to the run position and use a screwdriver to touch the power side of the solenoid to the small red wire on the solenoid the truck fires up and only runs while the screwdriver is connecting those two post. I've included a picture because I don't know the official name of the two post on the solenoid, still a novice please bear with me.

 

Don't know if this helps or not, but when my headlight switch was on, the starter would engage but there was no spark. Turning the headlight switch off the engine would turn over and had spark. It's almost as if when the headlight switch is on its taking power away from the coil?

 

So you did this?







If so, maybe your solenoid is gone.......

 

The only difference I did was the yellow wire I ran to the B+ terminal on the alternator. The truck ran just fine before I did the 3g swap. Is there anyway to check the solenoid?

 

Looks like you're missing the cabin power wire and it's fusible link. It would normally be under the battery cable side of the starter relay where you now only have the Red battery cable and the Yellow w/white wire from whatever. Is that your main charge wire? I know I've seen the color scheme before, but only on later trucks and can't remember what it was for.
The only Yellow w/white on a typical 3G installation would be the battery sensing wire to the 3G. But don't think it would be that large of a gauge wire.
Unless the picture is just misleading on my screen and that's just a normal size wire?

Anyway, you need your cabin power intact or you will experience what you have now. No power anywhere.
It has to be on the battery side of the relay, or the battery side of the Mega-Fuse if that's what you're using.

Oh, and if you are not already planning to, I would replace that starter cable pronto. Not that it's not currently working (you proved that) but it's going to fail someday. And we all know they like to wait until after 9pm on a Friday, after 6pm on a Sunday, or when you're 1000 miles from where you'd like to be. While running from chainsaw wielding, coverall wearing, toothless grin toting wildlings of course...

Paul

 

Yea the yellow/white wire is the main power from the alternator. What color and or gauge is the cabin power wire? This sounds like my problem. As soon as I get this straightened out, those older wires are being replaced ASAP.

 

It's usually a slightly larger (10ga maybe?) Black w/yellow stripe wire. Some are Black w/red, but mostly the older trucks. Yours is what year?
On my '79 there was more than one Black wire there, but only one that ran over the wheel well, heater/a/c box, firewall and over to the driver's side to a power terminal near the brake booster.

Easy to replace even if it's in bad shape or destroyed or missing in action. But if you didn't toss it, you should find it there somewhere.

Paul

 

EUREKA! That black/yellow wire is not attached to anything. Its 1040pm here so it's too late to test it, but im convinced thats the problem. First thing tomorrow I plan on doing doughnuts in my cul-de-sac!

 

Yup. It's the one you can see in this picture connected to the fuse near wheel well. It's harder to see, but the black wire connected on the other side of the fuse is connected to the hot side of the solenoid.

 

When that fusible link blew on mine, I first thought my battery had died stone-cold dead. You can't get ANY electrical action out of a truck with that wire disconnected, save for jumpering the S terminal on the solenoid and cranking the starter.