I am not the first owner of the truck. The engine was replaced (and heads redone) and an engine wire harness was replaced. I checked each wire for resistance, double checked my grounds and completed a negative volt drop test (first post).

Both the alternator and battery have been bench tested and despite a passing grade both have been replaced.

The overheating is a byproduct of the 40-60 amp draw, but it has not blown any fuses. Connected an amp meter while the truck was running and disconnected each fuse looking for the amps to return to normal. However they did not drop.

It should not reach 160+ degrees within 5 min's.

Next step is bench test the starter

 

Yes ..I think that it's the next step since it doesn't go through the fuse box. Also I don't think I read if you had and amp or not (aftermarket), that would also not be in fuse box (obviously).

I read you checked wiring, ok.... I hate making ppl answer same questions over n over, so sorry about that right there. Now I read in title that it's an '01 so then it can only be the 4.3 motor.... so starter would have a relay at least for switch...try unplugging that too to see if amp draw drops (you only mentioned pulling fuses not relays) though the main power will still go to starter.

 

I did some testing with my 2000 blazer just to see. I turned the lights on, had the four ways going, and turned to fan switch to position 4. Let the vehicle run and was just under 160 at 5 minute mark, actually more like 155 degrees. I have a charging system analyzer and with all this stuff on was running at 14.5 the whole time. If i turned rear defroster on, it would run at the high 12's lower 13. As for amperage, my tester allows me to apply a load onto the vehicle, and as soon as I did it started to show amps(it only does increments of 10) and the voltage would drop to low 12. Amps at the most would fluctuate from 10-30 when I applied to load manually. Without applying the load manually, the amp meter would remain at pretty much zero.

After about 10 minutes I had temps close to 210 on the case of the alternator, internal windings at the front of the case were pushing 230 degrees. Back shell of the case was well above 190. So I dont have the amps, or voltage issues, but I do have the temps right away it seems.