'02, 58K miles, battery light flashing while towing trailer in hilly terrain

[Fordina]

We were recently on a road trip in our '02 Astro with about 58K miles on it. We hit some very hilly terrain that we drove in for about an hour. We had 7 people in our Astro (5 of them small kids) and we were pulling a heavy trailer behind us. About half way through this terrain, the battery light came on for about 16 seconds. It later came on about 3 more times -- sometimes for about 16 seconds, other times it would just flash for about 1 second. No other problems.

On the way home, the battery light started up again in the same hilly part. The first time, it came on once again for about 16 seconds. Then, a second time for about 16 seconds. Then, a third time, just a flash of the battery light. No battery light in non-hilly parts of our 2 1/2 hour road trip.

One important note: on the way there, I forgot to put on the tow/haul button thing. I don't know if this had any effect on the battery light or not. On the way home, I had the tow/haul button on, but the battery light still started flashing.

Any ideas on this?

[old_master]

When the battery light comes on it is indicating that the alternator is not charging the battery. Could be any number of things causing it but most common is the alternator itself. Autozone and Advance Auto Parts will check it for free. Other things to check would be a loose serpentine belt caused by a worn tensioner, or poor electrical connection at the battery, alternator, body or engine ground. Just rearward of the underhood fuse panel there is a junction where several red wires come together, they have a habit of corroding also.