Alternator or something else? Please help diagnose
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Junior Member
Joined: Nov 2013
Posts: 7
Alternator or something else? Please help diagnose
Please help me diagnose my 2008 H3.
I couldn't start it after sitting on my drive way for a few days.
If I turn the key to ON, all dashboard lights come up like normal, when I try to start it, all lights turn to blank/off, key is locked. So I thought it was the passlock problem so I gave it a few minutes and turn the key back to ON, same thing, lights up, try to start, nothing and turns to blank. After a few attempts, it looks like the battery is completely dead. Turn the key to ON, nothing. No lights.
This is a new battery from costco a month ago.
So I took my jumper cable, hooked it up, a minute or two, I can start it. So I left it run for about 20 minutes, turn the key off, and try to start it, nothing. No lights.
Is this a bad alternator?
I couldn't start it after sitting on my drive way for a few days.
If I turn the key to ON, all dashboard lights come up like normal, when I try to start it, all lights turn to blank/off, key is locked. So I thought it was the passlock problem so I gave it a few minutes and turn the key back to ON, same thing, lights up, try to start, nothing and turns to blank. After a few attempts, it looks like the battery is completely dead. Turn the key to ON, nothing. No lights.
This is a new battery from costco a month ago.
So I took my jumper cable, hooked it up, a minute or two, I can start it. So I left it run for about 20 minutes, turn the key off, and try to start it, nothing. No lights.
Is this a bad alternator?
Super Moderator
Joined: Jul 2007
Posts: 13,056
From: Boat Town USA MI
Bad Battery? Just because it is only a month old to you does not mean it can't have a bad cell. Take it back and swap it for a "NEW" battery (see below).
Another thought..... a new battery does not always have a full charge after sitting for months. Whenever I get one for whatever (car, boat, truck, motorcycle) I charge it with a Deltran Battery Tender Plus (I have like 6 of them ... too many toys
).
Read the MFG date on the Battery before you pay for it, the months old ones are attempted to be pushed out the door before the brand new fresh ones at the back of the shelf.
and.... Let me finish with the old..... do you still have the OEM POS Battery Terminal Connectors??? If so, get rid of them ASAP, they are useless crap that cause more problems than most people can imagine. Feel free to search out the many threads on replacing the OEM Battery Terminal Connectors with a quality aftermarket set, like Stingers or your favorite brand. Cheap easy insurance to avoid electrical Gremlins. Kind of funny, when you do a Google search for Stinger Battery Terminal, look at the images and mine is always in the top row of results???
Another thought..... a new battery does not always have a full charge after sitting for months. Whenever I get one for whatever (car, boat, truck, motorcycle) I charge it with a Deltran Battery Tender Plus (I have like 6 of them ... too many toys
).Read the MFG date on the Battery before you pay for it, the months old ones are attempted to be pushed out the door before the brand new fresh ones at the back of the shelf.
and.... Let me finish with the old..... do you still have the OEM POS Battery Terminal Connectors??? If so, get rid of them ASAP, they are useless crap that cause more problems than most people can imagine. Feel free to search out the many threads on replacing the OEM Battery Terminal Connectors with a quality aftermarket set, like Stingers or your favorite brand. Cheap easy insurance to avoid electrical Gremlins. Kind of funny, when you do a Google search for Stinger Battery Terminal, look at the images and mine is always in the top row of results???
Senior Member
Joined: Jan 2015
Posts: 111
From: East Bay
Funny thing, 2 days ago I was writing on here how my truck is running great. Wife needed to use it today and I get that call "your hummer won't start". That's weird. I just did the plugs and throttle body cleaning this weekend. Truck was running perfectly. Doin had her put it on the charger. Maybe I left the dome light on last night. Took an hour and a half on 55amp setting to get it to start. After that I told her to leave it on the 10amp charge all day. She drives it many hours later and gets stuck at kids school. Now I'm out there, sure the battery is bad. And I bring my boat battery. Hummer acts the same way. Put jumper cables on it, after 16 minutes it's starts and I get it home. It won't start again. Has original terminals. Guess I'm staying home and changing those tomorrow?