Need help truck wouldn't start

Hi gang

So I drove to work this morning feeling good. Ran fine then went to lunch listened to my co worker talk his wife's suburban that's in the shop and gave Ole Phoenix a nice pat on the dash for doing me right 70k miles. Go to get in and go home nothing but a super fast flashin battery light in the dash. Friend jumped me started up drove it around and seemed OK voltage meter seems to sway a little driving made it 25 miles home. No issues turned her off would not start. OK bad battery thing is it was jumped twice before I left. First time cranked it with jumpers on maybe 30 seconds started up took them off and it ran then died down electrical went dim then back to normal then dropped and truck died. Jumped it again and no issues.

So get it home pop hood battery is reading 12.6 on my meter put the key in 4.5v reading. Do you all think it's a battery issue or alternator? Any good way to tell if you can't get it started.

It's 2018 5.7 with 70k never changed battery bought it with 19k miles

Thanks for help and input

 

I would definitely start with the battery first, its almost 5 yrs. old and our trucks do some funky stuff with a bad one. Good luck, and let us know how you make out.

 

Thank you will do but if I have to change the battery I want an AGM but don't know if that is a readily available and the fuse I need to get to make sure it charges.

 

Years ago my old 2007 had a battery die overnight. I came to start it in the morning and nothing. Jumped it off good to go. Let it sit more than an hour dead to the world.

I was always told big temperature changes kill older batteries. The beginning of really hot summer or start of a cold winter. They don’t like big fluctuations.

My battery had a dead cell in it and would not store or retain energy anymore.

If yours is over 4 years old it’s time for a new one anyway for peace of mind.

Once the truck is running put a simple voltmeter across the terminals of the battery. Voltage only 12v means alternator is not charging, voltage of 13-14v alternator is working fine.

The fact you mentioned 4.5v with key on makes me think your battery fell flat on its face as soon as you put a load on it and make it “work”

Replace it and report back

 

Yup. What he said! Spot on. We'll await the answer patiently.

 

Key on voltage drop is almost always a battery issue, 2nd would be a poor connection at the battery terminal. Considering how old the battery is replace it anyway and clean the connections.

 

Battery, if you get 4 years out of one you are lucky. Past time to replace it especially if you are in a hotter or colder environment.

 

Thanks gang pulled battery it was toast. Put a new one in checked reading 14v while running I think we are good!