this problem started about 2 months ago...

the first time, i had driven about 6 or 7 miles, then parked, and revved up a little bit. when the rpms were dropping down, they dropped to about 700 or 800 like normal, and then eased up to about 900-950. ok thats normal. but when it was dropping, the battery light and e-brake light came on, and then faded back out. the 2 lights were not even on for 1 second. ok whatever...

its been doing that ever since, but it doesnt happen everytime, maybe 50% of the times i rev up and then let the rpms drop. sometimes it will do it under the same conditions, sometimes it will do it under different conditions, for example, if i rev up in neutral and the rpms fall, but dont fall past 1000 rpms, the lights will still flash on and then fade out.

the afc reads the battery voltage, and its always different. sometimes it will be about 13.7 or so, which USED to be the normal voltage. then sometimes it will go as low as 10.9, although on average it stays around 12.2 or so. ive checked all wires, made sure everything was tight, and i just replaced the alternator with a rebuilt(refurbished?) one about 1 year ago. i have an Optima red-top that has been relocated to the trunk. there is a sticker on the side that says 10/05, i was wondering is that like an expiration date or a manufactured date?? one other thing, my trunk leaks, and water gets in there. the trunk is completely gutted, and the battery sits in the spare tire hole, on top of a thick rubber pad(was like this when i got it). water will leak into the trunk and collect around the battery and cap(for the sub). the battery has never been completely submerged though. today it was like an inch deep with water. could this have anything to do with the problem? sorry about the long thread, just trying to figure this out. does anybody know what it could be?

cliffs:
battery light comes on briefly when rpms drop
does not do it all the time
optima red-top battery with sticker that says 10/05
trunk is gutted and water leaks into trunk, surrounding battery

 

also, turning the headlights on drops the voltage.

 

i had a problem like this before, i couldnt track it down at all, and it kept getting worse and worse...i put a ground from the intake manifold to the firewall and it fixed it lol

 

yeah it seems to be getting worse also, but i dont know if its just me or not. when you put a ground from the intake to the firewall, was there a wire already there that had come loose or something, or did you do it all yourself?

 

on my car specifically there wasnt a wire from there originally...but you need more than just the ground on the starter.