If anyone has experienced this, I would appreciate hearing from you and how/if you resolved it.
During the hot summer months in Florida, the battery light keeps coming on after perhaps a half hour or fifteen minutes of sustained use of the AC and blowers running at full speed when driving from point A to point B. After arriving home, the battery is plugged in to a float charger overnight and continues to be fine. This has been going on for several years now. ‘Have replaced batteries and alternators to see if it improves. No change after batteries and alternators replaced. The auto parts store performed bench tests (under load) on the removed alternator and battery, and they said there was nothing wrong with them. The AC is kept on “automatic” and is set at 71F / 22C. Cabin filter is clean. The voltage measures 14.3v when engine is running, and battery above 12v when engine is shut off. All batteries were good quality with a minimum 5-year guarantee. None died overnight if I didn't put it on the float charger. During the fall, winter and spring, the light never comes on. Rather than make speculative guesses as to what might be going on here, perhaps those of you that might have experienced the same dilemma may be able to shed some light on this. Thanks much.

 

Have you replaced both battery cables? This is a maintenance item on these cars as they go bad every few years. Do both at the same time. Buy several extensions to get to the alternator bolt

 

Yeah, it's your cables. They deteriorate with age on the inside. You can tell by touching the terminals after driving a while. If they are extremely hot, this is your problem. Getting to that alternator bolt for the positive one is a real joy.

 

Thank you to Spikepago and foxbottom for your prompt and very useful suggestions regarding the battery cable replacement. 'Didn't realize that resistance and conductivity would be compromised with the aging of those cables. It makes absolute sense and is a very inexpensive way of trying to arrive at a solution to the symptom. 'Will replace both cables as suggested and comeback with an update in a couple of weeks to report on how it worked out. Thanks again!

 

You won't think it's so inexpensive when you see how much those cables cost ................