I charged the BAT and I get 12V at the BAT. With the key in the ON position I get no voltage with thte large lug on the ALT and ground. SO It is a fusible link. Now what?

 

i know you are not getting 12 volts at the alternator because you fusible link is blown because the alternator was putting out 45volts when running. your alternator should have 3 wire that deliver positive power to the alternator. the 2 smaller ones should only be delivering power when the key is in the on position. 1 of those 2 wires going to the alternator goes to to the voltage regulator and the other goes to the voltage or amperage gauge.

 

Start with the wire at the large lug and trace it back to the battery. Look for a segment of the wire that looks like it changes diameter. If you take voltage readings as you go along the length of this wire you will know when you have passed the fusible link because you will suddenly have a 12 volt reading (battery voltage). When you know where you have 12 volts and where you lose the 12 volts that is the fusible link.

An operational alternator should not put out 45 volts under any normal condition so I think that alternator is bad in addition to the fusible link being blown. You will have to replace the fusible link and pull that alternator off to have it checked before you run the truck or you will burn up the new fusible link also. Do not I repeat DO NOT replace a fusible link with a regular wire unless you are ready to replace all of the wiring in the truck after you put out the fire.

 

Thanks guys. I appreciate the help.

 

Fixed, fusible link off the main harness. What looked fixed was actually a severed wire. Replaced it with a 3 dollar fusible link from Autozone. What a bunch of crap. Thank you for everyones help.

 

so is it running good and no longer putting out 45 volts?

 

I really cannot account for readings like that. They ran the ALT on a bench tester at the shop and it was perfect. I am getting 14.3 at the BAT running. But before, while while running and testing the large BAT lug on the ALT, and the bolt on the exhaust manifold, I got around 50V. No idea.