- Voltage drop at both side are around 25 millivolts (that is Millivolts not Volts). So I think entire circuit is in excellent condition. For + I connect with probes positive terminal of battery with that screw that is at top of that red plastic at alternator. For - side I touch alternator body and negative terminal of battery.
-For record I finish electrical physic with grade A at university and I guess I know how to check voltage drop and understand it.
-"body ground strap, located under the truck, it looks like a braided cable."
I did replaced it today to with that dick so called starter cable.
- Replaced old alternator, bring one from U pull, then bring another from u pull. Checked old and second alternator from U pull and they show be good. Checked battery too and is good.
- I believe now problem is in control circuit that go to voltage regulator. Fuse 11 look good. I will bring a car electrician soon and if he find what is wrong and fix I will let you know.
- To add when I did drove over bump (alternator sometime overcharge sometime do not charge) I spot battery light went off for part of second. I guess something is loose in control circuit. Now truck is stall in front of one of my projects as truck is in not charge condition.
- With alternator not charging and engine running I have almost all battery voltage with probes at alternator body and that red post. So I think entire charging circuit is good

 

Wow! Thats really good, especially if the circuit was heavily loaded. Did you have the high beam headlights on, the heater blower on high, and the wipers on high, etc, to load the circuit for a few minutes before taking your readings?

I'm inclined to agree with you. Did you do as Bluegrass suggested in post 14 and check the three wire connector and its pigtail on the back of the alternator to be sure they are clean and tight connections?

To check out the control circuit, unplug the 3-wire connector on the back of the alternator. Then with KOEO compare the voltage at the battery + terminal and ground to the open circuit voltage of the orange wire at the 3-wire connector and ground. (Wiggle the fuse #11 in the BJB while taking this voltage reading to see if it affects the voltage reading.) If the voltage at the battery and at the 3-wire connector is within a 1/4 volt of each other the control circuit is prolly okay. (You might want to pull the BJB apart to inspect the wiring where fuse #11 plugs in.)

While you have the 3-wire connector unplugged and KOEO, check the battery light. Normally with KOEO the battery light would be on, but with the 3-wire connector unplugged it should be out. If it is still on, that means that the battery light has found its own path to ground. (And when you hit the bump it may turn off momentarily if it loses this short to ground.

I would appreciate that. Hopefully he will also be able to explain how he found the problem.

 

I think I fixed problem. It was broken fuse 11. I did check a couple times before. I saw just a dent not crack in fuse so I didn't change it. Lets go in order

- Original alternator was made all lights in car brighter - darker. Checked voltage with engine running at battery posts 14,7 to 15,5 volts. I think this alternator is not good. Checked it 5 times two times said it is good and 3 times not good. Battery light was blinking from time to time.
- First alternator from U pull look best. I put it on and immediately had steady battery light. When alternator and engine run I heard slight metallic noise from alternator. Voltage at posts vas like 11,80 V.
I was in emergency mood, Sunday and I had to go to new project tomorrow. So I pulled u-pull alternator 1 and without checking it returned to u pull and bring u pull alternator 2

- Nr 2 was 90A and look good to. Nr 2 was checked good by an auto part store.
I installed it and started truck. Odd was that for a few seconds battery light was on actually and then turn off. So I drive to work for like 6 miles and all suddenly battery light turn steady on (not flashing like original alternator). Job site wasn't to far so I just drive there. I assume that fuse 11 brake at this point bat not sure. When I come to job site I just left my truck there and every day before job I just play with voltage drop. Al suddenly after 7 days of testing alternator start one morning to charge again but with wild 14,5 to 15,5V. At that point I did start read about voltage drop checking and checking of fuse 11. So I pull fuse 11, look good just small dent at it in bottom (tried to do picture for you guys but impossible from small distance).
As truck was charging (albeit overcharging) I drove truck home after 2 weeks at project 1.
At Saturday I drive to another project with battery light on (steady on from that Monday 6 miles point). When I start drive it was overcharging but somewhere at 2/3 of way I saw dash voltage gauge falling down. I barely managed to come to project 2. Charged battery in homeowner garage and left car there until done.
- Today I decided to bring 3. alternator from U pull. When I was there I pull out a few 20A and 15A fuses. Went to truck and replaced alternator U pull 2 with alternator U pull 3. Turn engine on, battery light on and alternator didn't charge. Just to do something I replaced fuse 11(although I didn't see crack just small dent) and immediately battery light went off and voltage at post is steady. At first check it was 14,41 and 14,42 and at second check after driving home it was 14,38 and 14,37. U pull 3 was checked good by an auto electrician shop.

So to sum. I believe original is bad. As is nr 1 u pull. Nr 2upull is odd. Why did overcharge and have same symptoms like original? If will fuse nr 11 blow again I will let you know.

Just checked that fuse with ohmmeter it give me 0,L. I guess will check fuses next time with multimeter too, do not believe to eyesight.
Fuse 11 in this case denied logic. In theory it can only work and then brake. Evidently it did brake and start work for a while and brake again. Look possible to me as crack at fuse is impossible to see with aye.

 

A few years latter one of contributor of this mess was that single wire harness that go in alternator. When battery symbol start intermittent blinking I just add dielectric grease at top of harness of that single wire and blinking stop. I have to do once per year.