Long shot
- Thread starter ryanelwood
- Start date
If I remember right the 506 circuit had a short in it. I would have to look at my receipt to be sure though.
The charge wire on my truck runs back through the red junction box above the power steering pump and ties directly to the positive battery cable that runs around from the driver's side battery to the starter. I believe that wire has a fusible link built into it, but there is no fuse anywhere that I see. As I recall, every truck from 01-07 was designed like that. They changed it with the LMM.
There's a bulletin out for that. Stating if the ECM doesn't see voltage on that circuit it will inhibit charging. However I have NEVER seen that happen nor do I believe it.
Just something simple and stupid to look for that bit me in the ass. Make sure all the points where the alt bracket touch the block are clean and the bracket and alt are grounded properly. These trucks are really finicky with grounding issues. Just a quick way to check it is run jumper cable from the case of the alt to the negative on the battery to ground it out. If the system charges, then you have your issue.
When I had this issue, I never once saw a "Low Battery night" Just a lot of weird codes.
Hope it helps
When I had this issue, I never once saw a "Low Battery night" Just a lot of weird codes.
Hope it helps
I'm sad to say that I never got a chance to check anything. I had a battery charger on 2 amp deep cycle all night last night so that I could make the 15 minute trip to and from work today as I had no other mode of transportation. So on my way home from work all of a sudden my truck started to charge, I got home and put the multimeter on it to make sure I wasn't being tricked and sure enough it was charging. So evidently it fixed itself...I'm not sure what or how but it did. It does have me a little concerned but I guess I can't complain, for the time being I have a fully functioning truck, if you guys have any thoughts on what's going on I'd love to hear! Thanks for all the great tips and info I've already received its greatly appreciated!
sounds like you had a loose wire and hit a bump just right to create a connection. Might want to check for loose wires.
http://www.justanswer.com/chevy/7k3a2-lb7-code-po380-head-gasket-r-r.html
Josh,
I will post a link to the gm bulletin for the 175 amp mega fuse.
The lmm have the fuse on the passenger side firewall.
On lb7 as the op has and is listed in the bulletin, the megafuse is under the ubec case.
This is a common problem.
In fact the loose connection could have been a solder joint in the ecm.
Hopefully the truck is no longer a problem.
Josh,
I will post a link to the gm bulletin for the 175 amp mega fuse.
The lmm have the fuse on the passenger side firewall.
On lb7 as the op has and is listed in the bulletin, the megafuse is under the ubec case.
This is a common problem.
In fact the loose connection could have been a solder joint in the ecm.
Hopefully the truck is no longer a problem.
I checked for you about the computer being the culprit. It could cause that to happen but since it has started working again the ECM definitely is not the problem. ECM has to recognize the signal for alternator to charge. You must has a loose connection or a bad alternator.
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I'll post the wiring diagram for the charging circuit as a reference for anyone else who is looking for information on it, but as you can see, the alternator does not charge back through any 175A fuse. There is only a fusible link in the charge wire.
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Josh, I'm certain you're correct because I've replaced all of that wiring on my truck. I'm pretty sure I would have noticed the large fuse along the way.
Is the plug plugged into the alternator? I changed mine out not too long ago and forgot to plug the plug back in
I'll post the wiring diagram for the charging circuit as a reference for anyone else who is looking for information on it, but as you can see, the alternator does not charge back through any 175A fuse. There is only a fusible link in the charge wire.
You are correct Josh. Upon looking at it I remembered you didn't need the fuse there to drive/use the truck. It doesn't effect the charging system only the glow plug/intake heater.
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Ok josh,
I will have to check out my train of thought here.
I just had it in my mind when that megafuse blows the alt does not charge.
My techs have had it happen before on several occasions.
And we found no charge and popped megafuse.
Maybe it effects something else. Or is not directly charging through the fuse.
I will try and research a bit more because I feel very certain on this.
But from your schematic it does not make sense.
Why does the bulletin list the 175 amp fuse as well?
I will have to check out my train of thought here.
I just had it in my mind when that megafuse blows the alt does not charge.
My techs have had it happen before on several occasions.
And we found no charge and popped megafuse.
Maybe it effects something else. Or is not directly charging through the fuse.
I will try and research a bit more because I feel very certain on this.
But from your schematic it does not make sense.
Why does the bulletin list the 175 amp fuse as well?
I've replaced the charge wire on my LB7 and besides the fusible link it definitely didn't go to a giant fuse. Perhaps a problem with the glow plug circuit can blow the fuse and kill the alternator?
Ok josh I got it.
The alternator does not charge through the fuse but if the fuse pops the alternator doesn't charge.
No bs man all these years I never looked that deep into it.
I just knew after working on a truck and it didn't charge it was always that fuse.
I guess I just thought life was that simple.
Ignorance is bliss, and now I am ruined!
Thanks buddy
The alternator does not charge through the fuse but if the fuse pops the alternator doesn't charge.
No bs man all these years I never looked that deep into it.
I just knew after working on a truck and it didn't charge it was always that fuse.
I guess I just thought life was that simple.
Ignorance is bliss, and now I am ruined!
Thanks buddy
I have a 03 GMC 4500 new alternator new batteries it charges sometimes sometimes it won't I took it to the shops they put it on a machine and alternator is good I'm coming to the collision I think it is the computer everything else checks out what do you think