my battery light in the message center comes on only when is hot outside, last summer it was doing this, and winter it stopped, now that the warm weather has returned so has the battery light in the message center? any one know what this is about? the guage also is reading normal. 2001 GMC Serria Duramax

Probably a bad diode in the alternator. Possibly a fading cell in one of the batteries. Autozone and maybe some other stores will check both out for free, though I think you have to take the alternator out. Ask them first.

You don't necessarily have to buy the parts from them if they check bad but, that is why they offer that service. Their alternators aren't that good, you will access that lifetime warranty, probably every year. They do sell fine batteries though, I got my Optimas there.

Good Luck.