2004 Blazer 4x4 153k miles.
It started yesterday, I was driving on the interstate and then my battery light came on and only had about 11volts showing. She was still running perfectly fine and when I got off the interstate and went to go after a red light, volts came up and was good. I made a couple of about 1 hour errands last night, would go out, she cranked perfectly fine but would only show 11 volts for the first couple minutes. Well, today on my way to work (about 25 miles almost all interstate) volts never came up past 11. Then as I got closer to work, volts kepts dropping until about a half mile from work, gauge cluster shuts off. I was able to make it to work. She was still running completely normal. I parked in my parking lot, still running fine. I turned her off, and then she wouldn't crank back up. So would it be the alternator, battery, or some other even more fun electrical problem? Any input would be great... Thanks y'all!

 

I would first check your belt, make sure its not broken ect causing the alt to not charge.
otherwise, I would start looking at your alt. Take it to an auto parts store that tests those things, and get it tested.

 

Check for lose or dirty wiring also

 

I glanced over the wiring and it all seemed to be attached properly. I will check again. I was hoping not to have to take the alternator off to check it but it is what it is. I'm not the most mechanically inclined, but I have changed alts before. Is there any good picture reference for changing it? Thanks

 

Pretty simple to diagnose.Charge the battery first.Attach a volt meter to the battery,note the volts and start it.If they come up to 14 or so,the alternator is working.The battery terminals are prone to corroding under the connecting caps,so you need to take the terminals off and inspect.That would be the first suspicion since it sounds like the problem is intermittent.Probably not the battery itself since it ran for a good time on just the battery.The Blazer/Jimmy alternators are a common problem and fail regularly.

 

Well, I have been at work for about 7 hours now. I went out just real quick to check to see if she will start. After gauges shot off this morning and not turning back on right after I parked... She started now. Started off having 11 volts according to the gauge... But only after a few seconds.. the gauge went up to past 14 to almost probably 15 volts. Cranked a little slow but nothing major. Let her run for a couple minutes before I had to go back in. Checked all the battery cables, they were tight. Checked alternator wires. They too seemed to be tight and not in bad shape.

Fuse problem? I didn't get a chance to check so no idea.

But if it was the alternator, wouldn't the battery have been drained quick on the interstate, while listening to the radio, blasting the heat?

If it was the battery, how would it randomly recharge?

Dang I hope it isn't some even more expensive electrical problem.

 

sounds like the alt,i have a 2000 chevy blazer 3.4L and mine was going from 14 volts then it drop to like 10 and the battery light come on everytime...I charged the battery and after a few min it go back to the same thing..it go back and forth fluxuate from 14 to ten then back to 14 then it drop again.Replaced the alt and that was last time it did it.charges fine now with no prob at all..So first thing i check be the alt...

 

this is for a 2000 chevy blazer hope it be the same as 2004

 

I took it to Advanced Auto yesterday after work and she was flat lining 9 volts coming in. They checked it and of course alternator. Changed it in about 25 minutes and now shes running just fine! Thank yall!