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Boost Junkie
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Discussion Starter · #1 ·
Long story short, noticed that the alternator was going bad, so changed the alternator, which worked for a couple of days. Now the charging system light on the dash comes on a couple of minutes after the truck is on.

Post on the alternator shows ~15v KOEO
Both batteries show ~15v KOEO
Both pigtail pins show ~15v KOEO
Monitor shows ~11-12v KOEO
Continuity between alternator and positive battery posts is good, as is ground posts and the chassis

any ideas? because I'm about to light it on fire... :(
 

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Boost Junkie
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Discussion Starter · #2 ·
Also should probably note that all voltages were taken after the glow plugs shut off...
 

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Administrator
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the light can be low charge or overcharge 15 volts is high are you sure ?

also I think We talked about parts house rebuilt alternator quality before ?
if not they are notorious for not working on a60 superduty properly
 

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Boost Junkie
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Discussion Starter · #4 ·
yeah, checked it over two days with a DMM. Given the fact that the monitor is still shoing ~11-12 and the batteries aren't charging for anything is what's giving me fits
 

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Boost Junkie
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Discussion Starter · #6 ·
No, the truck hasn't died yet, but I'm hesitant to drive it real far in case it decides to let go...

But like I stated earlier, it's not charging either
 

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i'm just going to say there is no way IMHO your batts are 15 volts key on engine off

if the alternator has not been charging them for even 1 glow plug cycle / start/ run

but u would want to throw a known good DVM on the output post of the alt when starting and running to see what it's doing and really verify it's the Alt and not a connection

monitors tend to read lower than the actual output from what I have seen
 

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Boost Junkie
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Discussion Starter · #8 ·
Long story short, noticed that the alternator was going bad, so changed the alternator, which worked for a couple of days. Now the charging system light on the dash comes on a couple of minutes after the truck is on.

Post on the alternator shows ~15v KOER
Both batteries show ~15v KOER
Both pigtail pins show ~15v KOER
Monitor shows ~11-12v KOER
Continuity between alternator and positive battery posts is good, as is ground posts and the chassis

any ideas? because I'm about to light it on fire... :(
EDIT: fixed

Ah, ZMann, you sir would be correct, engine is running, not off, so KOER?
 

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the battery is at 15 volts engine off>?
 

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mech 1
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14.7 should. Be max voltage not 15 that is never seen any vehicle run with that high of voltage unless their running optimus battery but the alternator should still regulate it to no more than 14.7.
 

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i had the same problem, first of all make sure the batteries are good & if they have been drained like that give them a deep cycle charge because an alt will never revive them. also get a good alt. because i got an autozone one & it sucks. kinda looking to upgrade to a performance one.
 

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Boost Junkie
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Discussion Starter · #15 ·
Well, here's where I'm at, the batteries out of the truck both come out to ~15v, I've started hunting for grounds/drains in the system to see if that could be an issue, but when I went to start the truck this afternoon after I got off work it refuses to start... drove fine all the way home, now no crank/no start...

ugh...
 

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Discussion Starter · #17 ·
alright, I'm suspecting a short to ground somewhere in the system now, went out this morning to put the batteries on the charger since weather last night but a damper on trouble shooting...

both batteries are somewhere around %40 according to the charger

any common things to ground out?
 
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