I first picked up the truck in January, 160k, 3.4L XtraCab etc...
On the drive home, the battery light would come on and the headlights would dim. Get on the gas a bit and both would fix themselves. A friend and I tested both the battery and the alternator and found no problems. Battery appeared to be fine and the truck would run on just the alternator after pulling the battery. After a month, the issues hadn't gotten any better, but no worse either, every so often the light would come on, but it wasn't something I could voluntarily replicate.
I installed an amplifier and woofer, nothing huge, just a 500W peak/350W RMS. It worked fine for a few months up til now. Recently the sub would cut out while driving and then come back on. The light on the amp remains on. Its not the remote wire for the amp, i've jumped the battery lead with the remote to test that. All wiring hasn't changed and sometime works and sometimes doesn't. Yesterday, it just started now working at all. The light on the amp is still on and the fuses are fine.
I've got no other auxiliary lights/winch/gps type devices drawing any extra power.
Friend mentioned that it could be either a bad battery, or maybe a grounding issue for the battery. I've got two questions:
1. I know there are multiple locations for the battery to be grounded to the body/frame/engine block, but where are they?
2. Are there any other possible problems?