I woke up today and the truck wouldn't start. I read the posts and followed the advice. I changed batteries and it did start - however, the battery idiot light keeps flickering on and off. The battery guage is on the high part of the good range.

My other battery was also showing on the high part but when I started it, it went down to the low end of the guage.

What should be my next step?

Thanks

 

Did you check your battery cables for any corrosion? Even a little can make a difference. I'd get a wire brush and clean the cable clamps really good.

 

yes, I did that. I just drove it over to the parts shop and the alternator tested that it was barely charging the battery.

 

Sounds like the voltage output of the alternator. Normal alternators put out around 14 volts when charging, if the alternator isnt putting that much out then you're alternator is bad.