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Charging System Problems PLZ HELP (I'm BaKed)


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hey guys been a long time since i have made a post....well i am having the same problem i was having with my 79 620....i replaced my alternator and my battery and my charging system is still not working....i ran a new ground to my battery and pulled the positive off and my truck still dies....my voltage reg is internal so my alt passed when i started seeing the problems again after about two weeks of repair....i am completely lost about this and if i can figure it out soon i am gonna be posting my truck for sale....plz help me thats my last resort.....and if anyone might have had the same problem plz gimme some info on what you did....i cant figure this shit out

Edited by datzenmike
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Where are you getting the alternators? I found that most of the "lifetime warranty" Kragen or Autozone alternators had a 75% DOA rate. Of the remaining 25%, most of those lasted less than 6 months. I had one last a couple years...


And yes, many of those "tested" good.




In one odd case it turned out that I had no connection between the battery and alternator- the wire was broken in the harness. It would READ OK unloaded, but with any load it was essentially an open.

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the guys upset.. lets look past the title.. :D


anyhow i would double triple check the wiring, i had a problem for a long time where i could only drive in the day, if i turned the head lights on my battery died.. turned out i just had some crappy connections, cleaned em up an i was fine..


dont let it get to ya man.. you'll figure it out..

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hey guys an update for you....so i spliced a spare wire into the output of my Alternator....this means i bypassed my voltage regulator....i know this isnt rly safe but its getting me from point A to B....i run my stereo electric fan and headlights so i can keep the battery from overcharging....any suggestions on why this works....also if you have an spare wiring harnesses that would be a plus 2

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How can you bypass the regulator? It's internal to the alternator, per what you said and the year of the truck. No way to bypass it.


Is it possible you have a non-regulated alternator in the truck, which is supposed to have one?


If it's overcharging AND it's internally regulated, the internal regulator is blown. Had that happen, and yes running the headlights kept the voltage down.


One sure fire way to destroy the internal regulator: Disconnect the battery when it's running.

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on my 77 620, someone hooked the wires backwards on my altinator. After I bought the truck, I swapped the wires on the altinator and started to drive it. Lights were super bright.... I didn't realize that I was getting 17+ V out of it until the battery started to smell like a septic tank. I put a new voltage regulator in it and it started to work right.


On all 3 of my running 620's, I've had a loose belt cause charging issues.

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have you checked to see if its got a draw or something? maybe groundin out somewhere.. this might sound funny... check your head lights.. my problems all started because of one of the connectors on one of my head lights snapped off an it would cause a draw, which killed my alt and or volt reg..

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