20 gauge Beige w/blk stripe-has an unknown rubber rectangular box and oval plug inline with the fusible link, make a long story short, had an electrical short from my horn and burned up the fusible links-my questions is would it be ok to replace the wire with an 18 gauge wire with a new fusible link and be good ?

 

It's always ok to go larger on the wire size. Just make sure you use the correct fusible link.

 

just concerned about the rectangular box and plug thats on the wire-some sort of a diode or resisitor and weather it's needed ?

 

Not sure what that is. A picture might help. You could also try in the 77 forum for your pickup and see if someone recognizes it.

 

replaced the bad voltage regulator and sta wire from alt to solenoid and new fusible links-charges great 14.7v @ 1500rpm but the alt idiot light is still on-wondering what triggers the light on the dash ? Theres also an oval condenser looking peice grounded to the voltage regulator with a wire going in and out of it, wondering if that is the culprit ?

 

The idiot light is triggered by the voltage regulator. The light is not grounded, it should be in a plastic socket with two wires. One side of the bulb goes to the ignition switch power. The other side goes out to the "I" terminal on the voltage regulator.

When you turn the key on, but the engine is not started, the voltage from the keyswitch goes through the idiot light bulb, lighting the bulb and also triggering the regulator to put the alternator "online" to charge the battery. It does this by the small leftover voltage it gets from the "I" terminal which comes from the bulb.

As soon as the alternator starts turning and charging, the voltage regulator recognizes this, and it puts 12v on the "I" terminal. 12v on both sides of the bulb turns it off. If the alternator goes bad or you throw a belt, the voltage on the "I" terminal will drop and the light will come on.

The condensor piece is for radio noise. It hooks to the yellow wire on the "A" terminal of the regulator. That's it's only purpose, is to help get rid of the whining noise you sometimes hear, especially if you have a tape player. You can usually hear it slightly when there is no song playing on the tape.

 

wondering if this aftermarket advance auto bwd voltage regulator is the cause for the light still being on-it's much smaller and lighter than the original and the plug fits much looser but terminals are the same-I couldn't get a charge by just replacing the bad voltage regulator and alt. I replaced the sta wire and links in and out of the starter solenoid and now it charges. I guess the next step if it's not the regulator is to remove the factory electrical tape from the I terminal from the regulator til I find something odd ?

 

Unplug the regulator and then turn the key to run without starting the engine. If the light doesn't burn, turn the key back off and then plug the regulator back in. Then turn the key to run again without starting the engine. Just checking to see if the regulator has control over the light.

If the light comes back on, I think your theory may be right , the regulator is causing the light to burn.

 

I unplugged the regulator and no light even while running, then I went and plugged in my bad original and steady light just like the new one-I'm going to get a motorcraft one and hopefully it shuts the light off-What else I noticed is the new one is electronic and my original is mechanical, that's probably the issue

 

The electronic one should interchange. You might have trouble finding a mechanical regulator.