Quote:
Originally Posted by VetteVet
Well no replies yet so let me see if we can unravel this mystery. I quoted your post so I can bold the things I have questions about.
1. How are you getting power to the cab I assume off the J block since you only have 1, 4 gauge wire from the alternator. Same with the 8 gauge wire off the starter solenoid which also serves as the battery charging wire.
2. Does this mean that you blow the fuse just by turning the key on or does the truck have to be running. This is important to know, because if it's blowing just by turning the key on, it means that the circuit is shorted .
It also figures that the circuit is not shorted, because it is hot without the key on, so it would blow the fuse anytime the battery was connected.
3. If it's blowing while the truck is running, Which I suspect, it means that the maxi-fuse cannot handle the amp surge draw when the electrical loads kick in, and you may need to replace it with a rated fusible link like the one shown in the diagram.
You really don't know if the BATT stud on the alternator was shorted to the case (ground), before you fixed it. Do a continuity check on it and wiggle it around while you are checking it because the engine motion and vibration could cause it to short to ground while it was running.
While we're here you should check all the power wires to be sure they can't touch grounds while the engine is running and if the insulation is good on them. Example: any wire or cable that could be touching the exhaust.
Your two tests with the voltmeter are not much help because they only show voltage drops on the two wires you tested, and .2 volts is not much. Also were they taken with the engine running or Key off or key on.
The best thing you could do is put an amp meter on the alternator output line, and see how many amps are going to the maxi-fuse with the engine running at about 2K, while you turn on the accessories.
4. I'm guessing that the power accessory CB is not a factor because it probably doesn't come into play until your relays are closed by being switched on. How did you check it? engine on or off. Key on or off.
5. Another thing, did the engine die when the fuse blew or did you just see that the alternator quit charging. It would have quit charging when the MF blew but if you had a huge draw on the battery it would have blown the fusible link in the battery feed wire to the J block.
This leads me to believe that the alternator might still be shorting.
That's about all I've got until until I hear more from you.
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Thanks for the reply Vette. Ill list off my answers with their questions you have.
1. You are correct with your assumption. The power for the cab is coming from the jblock.
2a. Initially, the fuse would blow right when i started the truck. But i figured it was the connection at the BATT stud shorting from a loose connection or the stud itself being loose. I replaced the stud and it seemed to fix the fuse blowing on start up. Then i put it in drive took off down the road and looked at my voltage gauge and it was reading way low. Come to find out the fuse blew.
3. From my previous thread, i believe you helped me with, you suggested the 40amp maxi fuse. it's been running perfectly well since then. I have tried the fusible link setup but it seems to get hot quick. Thats why i have the 4g with the maxi.
The tests from my OP arent showing the numbers that i received. My numbers were coming out to 2x what they show.
Alt BATT stud to battery + = .2
Alt case to battery - = .4
Sense term to battery + = .3
4. I checked the accessory CB with key off. Positive cable removed and the test light in between the cable and the post.
5.The engine continued to run whenever the fuse blew. The voltage just dropped.