Alternator brand new but not charging battery
[size=16px]Just to kind of summerize this thread, the problems my 2007 Hummer H3 base model was after changing the alternator it stopped charging my battery. No CEL. Only a battery light which accordin to all my studying a battery light on an H3 is actually the light for your alternator charging your battery. I also installed a new alternator plug wire, the 2 pin harness. I checked the alternator with my truck on and it was working, I tested both sides of the new plug I put, I had power at both sides of the butt connector so I knew it was good. I'd get a service charging system and service stabilitrak and when the battery would get really low while only about an hour of driving around the abs light and message would pop up, but never a CEL for this issue. I almost bout a $450 from Autotech Alternator and or CAS Car Audio. They had the best deals. GP Car Audio always has good deals but wanted damn near $700 for a high out Alternator. Even if I did have the money I would buy that. But I always start with cheapest option first when the problem isn't as forthcoming as say a flat tire or blown head gasket and it's never ever worked out until now so I'm pretty stoked. I hope this helps someone in the future. If you have the same symptoms after changing yoir alternator or even if not just go change the stupid Mega Fuse. Your welcome lmao. Thank you guys for all the help. And Doc yes I did upgrade my batt terminals. I'm a car Audio guy so those always get changed first lmao. Now on to finding a new front diff. Yayy me.[/size]
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Joined: Jul 2007
Posts: 13,090
From: Boat Town USA MI
[size=16px]Just to kind of summerize this thread, the problems my 2007 Hummer H3 base model was after changing the alternator it stopped charging my battery. No CEL. Only a battery light which accordin to all my studying a battery light on an H3 is actually the light for your alternator charging your battery. I also installed a new alternator plug wire, the 2 pin harness. I checked the alternator with my truck on and it was working, I tested both sides of the new plug I put, I had power at both sides of the butt connector so I knew it was good. I'd get a service charging system and service stabilitrak and when the battery would get really low while only about an hour of driving around the abs light and message would pop up, but never a CEL for this issue. I almost bout a $450 from Autotech Alternator and or CAS Car Audio. They had the best deals. GP Car Audio always has good deals but wanted damn near $700 for a high out Alternator. Even if I did have the money I would buy that. But I always start with cheapest option first when the problem isn't as forthcoming as say a flat tire or blown head gasket and it's never ever worked out until now so I'm pretty stoked. I hope this helps someone in the future. If you have the same symptoms after changing yoir alternator or even if not just go change the stupid Mega Fuse. Your welcome lmao. Thank you guys for all the help. And Doc yes I did upgrade my batt terminals. I'm a car Audio guy so those always get changed first lmao. Now on to finding a new front diff. Yayy me.[/size]
Welcome to Hf and hope to see you around here again.
Senior Member
Joined: Feb 2021
Posts: 265
From: New Mexico
Dang, yeah a blown megafuse won't let the alternator charge the battery and will give all the symptoms you described. I assumed when you said you tested the alternator you were measuring at the output.
Any idea what caused the fuse to fail? There's a lesson learned there worth sharing.
Any idea what caused the fuse to fail? There's a lesson learned there worth sharing.
Senior Member
Joined: Feb 2019
Posts: 300
What does the MEGA FUSE look like?
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