I have an '89 F150. The "low battery" indicator light keeps coming intermittently while driving. I took it to a local parts store, had the battery and alternator tested. They were both good. The battery is 3 1/2 years old. I cleaned both terminals really well and sprayed it with contact cleaner. The truck fires up and runs well without a doubt. It's that "low battery" light that keeps coming on and is quite annoying. Have any of you experienced something like this before? Any help would be appreciated.

 

trying to figure mine out right now. Mine is doing the same thing I'll get back to you if I find a fix. I have a new battery and the Alternator is doing it's job. I'm going to check where the ground is connected to the body make sure it's tight when I get home.

 

I know it's been weeks and I solved the problem by replacing ALTERNATOR on Aug 5th. Before hand, I cleaned battery terminals, replaced both + and - cables one by one. Problem was still present. So I replaced voltage regulator which was an internal type. Well that made the problem worse. I F***ed the springs and brushes when I took the old one out. The spring/brush assembly kicked my ***** trying to put it back to together. So I finally broke down and bought a new alternator and PROBLEM SOLVED! Spending almost $100 on a new alternator was my very last resort; however I eliminated the bug. I guess it was meant to replace it since it probable original via old as my truck which is 27 years old. Thanks for all the help.