01 LB7 Battery Light On, Other Issues

[LB7Nick]

I searched and searched but couldn't find anything matching my exact problem. I recently replaced both my batteries on my 01. The day after I replaced them I started the truck and the battery light came on and none of the accessories would work (ac, radio, cruise, etc.) From what I've read nearly everybody whose light stayed on reported that their gauge showed less that normal voltage. Mine is showing over 14 at all times. The local autozone tested the whole starting and charging system and everything came back good. I decided to start checking fuses that I thought may be related but every fuse I pulled was good so I put them back in place. I started the truck after that and the battery light went away and everything worked normally for the rest of the day. Tonight driving home I had the cruise set, everything working fine then the battery light just came back on, cruise, radio, and heat turned off. I'm not sure where to look next. Any ideas?

 

[Kappa9012]

how far over 14v? Do you notice dash or head lights dimming when it happens? Any codes at all? Have you checked to see what the actual voltage is when the battery light is on?

 

[MACKIN]

If you pulled fuses and it solved the problem perhaps try doing one at a time and isolate the possible short.

 

[LB7Nick]

Just an update, today I went out to mess with it and started the truck and the battery light was off and everything was working. I don't get it. I tested the voltage at both batteries and both were showing 14.95. So I guess now I'll wait till it does it again and if it does go from there.

 

[PhilsLB7]

I tested the voltage at both batteries and both were showing 14.95.

The battery voltage will be the same at both batteries if you didn't disconnect one of them. The batteries are connected in parallel so you have to disconnect one of the batteries to read the voltage correctly.

 

[LB7Nick]

The battery voltage will be the same at both batteries if you didn't disconnect one of them. The batteries are connected in parallel so you have to disconnect one of the batteries to read the voltage correctly.

Alright I disconnected one at a time and they're both individually reading 14.7-8. I think I finally found a correlation that somebody may be able to make sense of. I just realized that recently the light only comes on when I try to turn the ac or heat on. After that I can loosen the negative cable on the left battery and tighten it back up and the light will go away till I try to turn the ac on again. So now I'm looking for another arrow in the right direction, I've never really messed with any of this electrical stuff. Thanks for everyone's help.


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[mike diesel]

Did you check connections at the alternator? Possible corrosion as well.