88 F250 Intermittent Battery light

[Torqued]

I don't drive the truck very often. Just once every month or so with the camper. The last couple of trips the battery warning light would come on and go off intermittently. The voltage never varied when the light would come on. Turning things on or off didn't seem to have any effect. The battery seemed to keep charged just fine. I figured there was something wrong with the warning light but couldn't find any loose connections or any other obvious things. Any ideas?

[tony36]

your light won't come on until the voltage drops below a certain level. If it just flashes periodicaly then either the alternator is occassionaly dropping volts and is getting ready to quit, or you could have a loose connection on the alt. Probably the first. Your battery will keep charged fine if it is intermittent like it is now, but if it becomes more frequent and stays on longer then it will start draining the batt.

[Torqued]

Thanks for the reply. I figured as much about a low voltage causing the light to come on but I watched the voltmeter when the light would come on and go off and the voltage never wavered even a little.
The light would come on dim, flicker a little and then get bright and stay that way for up to 10 minutes while driving. Then it would fade out and start all over again after 1 to 10 minutes. On the second trip, it came on as I left the house then went out in a couple of minutes. Didn't come back on again throughout the trip (about 400 miles).
I was suspecting the alternator but thought the voltage would have to drop off if it was bad. I'll probably just buy a rebuild kit for it and keep it in the truck just in case.