charging system warning light

[thechase_52]

My charging system warning light has been coming on randomly for the past 6-8 months. Now it seems to be happening alot more frequent. It seems to come on when I brake or let off the gas. when i am accelerating or maintaining a speed it doesnt come on. My expedition starts just fine and has never stalled, so i am not sure what the problem is. Could it be the battery cables? Any help or ideas would be greatly appreciated!!!!!!!

 

[tonydiv]

The simple way to test it is to measure the battery voltage when the event is happening. If you don't have a volt meter with long leads, you can pick up a cheap tester that plugs in to the cigarette lighter that displays voltage with a series of led lights. It's not as accurate, but it will at least tell you roughly what is happening.
The voltage shouldn't ever fall below 13.5 when the engine is running.

I'd also poke around under the hood and look for loose or damaged wires going from the alt to the battery.

 

[panda24619]

also clean the battery terminals. this morning i went to start my truck and all lights were on and turn key. BAM! everything dead. my terminals were so green that no power was going to the ground. so i had to clean them. gotta put some dielectric grease on them.

 

[thechase_52]

i did look at the battery cables this weekend and the negative cable was corroded really bad. i cleaned the cable and didn't have the warning till this morning. popped the hood and the negative cable looked like i had never cleaned it. What causes the cable to corrode so fast?