Electrical Problems -- Battery Charging System Light On

Hi there,

Relatively new to the forum... used to own a '96 tacoma back in high school (recalled for a new lump sum), and bought a used '09 4wd base model this december.

i've put about 12,000 miles on it since i got it (travel for work often) and i'm at just over 85,000 miles. i recently installed a CB radio, (last wednesday), and after disconnecting my battery, I apparently did not tighten my negative terminal sufficiently. The next day, (thursday), I am driving for work, and my dashboard shuts off, and radio, then 10 seconds later turns back on before I can pull over. I proceed to pull over, and notice the negative connection is clearly detached. I reattach, and continue on my way. I arrive at my destination without further issue.

I return to the truck 4 hours later to begin my ride home, and notice the battery light is on, but flickering off and on every few minutes or so. When I return home, I think that perhaps my terminals are dirty, and clean them. Battery light goes off for 4 days.

On Monday, I am again driving for work, and as I reach my destination 200 miles away, I again lose power as I am pulling in the driveway. I clean the terminals again, and she starts up slow, but OK. battery light is on again, but drive back home 200 miles regardless.

So now I'm obviously getting somewhat concerned, as the issue is clearly not with the terminal. I go to my local NAPA and ask them to test the battery & alternator, alternator is putting out 11.6 volts with all accessories running. 11.9 without any. I bring it to my trusted mechanic, who agrees it is likely an alternator problem after testing battery & alternator.

I purchase a re-manufactured alternator, and quickly replace (surprisingly easy job). Truck starts up slowly, but runs. Battery light is off. I let it idle for 20 or so minutes while revving to 2000 RPM occasionally, then shut it off. I return 10 minutes later to try and start it, and battery is dead. I test the battery and it's not holding a charge. It's only 7 months old, but I had heard that sometimes replacing the alternator will short the battery... or something like that. So I go and buy a cheapo at WalMart, and she starts up fine, but battery light is back on.

Having to drive again 300+ miles again today, I opted to risk it and bring a jumper and the extra (but likely dead) battery, which I have charged overnight. The battery light was on the whole way, but flickering between bright and dark. This concerned me, but I regularly checked my voltage and it never dropped below 11.9 with accessories on, and 12.5 without. So I carried on my way, had no issues getting there. On my return home, still no issues. After an hour of driving, I stop to get gas. When I start it back up, without issues, battery light has turned off! Voltage is up to 13.7 w/o accessories! I drive home, and as I am in my driveway, I begin flicking the lights, radio, and fans off and on. They cause the light to turn on, but immediately turn off. I continue to do this for several minutes, and when I turn the A/C on, the battery light comes on and stays on. An hour later (about 2 hours ago), I start it up again, and battery light is off. Didn't test voltage but assume it is high again (in the range of 12.5 - 13.7).

So right now the light is off. I am convinced I have an issue with a ground, corrosion, or connection issue somewhere. My plan is to bring back to my mechanic and have them investigate, as I am not familiar with these sorts of things. But concerned about their earlier failure to diagnose, and don't really want to pay for electrical diagnostics ($90 an hour).

Am I getting close? Any advice on what connections to approach?

 

I'd start checking all the connections positive and negative. Disconnect the battery, and work you're way back from there making sure everything is clean and tight. Grounds to motor and frame. Positive to altenator and starter.

 

I would follow the ground wire to where it stops, unbolt and clean all contact areas, and reassemble . You might have more than one problem, but this is a easy one you can do yourself.

 

When you say "clean and tight" should I test them for continuity? Or if they pass the visual check, OK?

The ground bolt from the negative terminal looks ok... but does have a rusted old connector from what I was assuming a previous owner's accessory of some sort. I'll take another look tomorrow and unbolt/clean/reassemble as suggested.

Thanks gents.