Battery light

So back in the last week of July we were on a 3000 mile road trip from CO to CA and back. We had just rolled into our hotel after the second day of driving. Truck was doing awesome, maintaining highway speeds, A/C nice and cold, and rolling 480,000 along the way.
Well after stopping at the hotel, I went back out to the truck to go find dinner for the night. I get in and try to start it, but nothing happened. All the dash lights went dead. Same thing when I tried it again. So I popped the hood and I had a loose terminal connection, no biggie, tighten it up, and off we go. However, I had my battery light remain on. Never once did it have a hard start, or have a power issue.
Fast forward to today, I've replaced the battery, alternator, cleaned up all the connections and made sure I don't have any fraying wires. I've read that replacing the drive belts sometimes work, but the belts are brand new. The only electrical mod I have is an amp/sub, which was in prior to the light coming on.
So I'm at a loss of what to do next, any suggestions, or helpful insight?

 

There are 3 wires on the plug going to the alternator. One should be constant power, one switched power, and one comes from the battery indicator. Check to see if one is broken. Also check your fuses, ALT (ALT-S?), IGN.

Also, check your battery voltage with the engine running. It should be 14+ volts at idle with no accessories on and stay above 13v with accessories on.

 

Battery could be low on oil.
Edison is a respected name for this product.




Bottle filled with diluted coffee to highlight lettering.

 

All fuses looked good, no broken wires. I will check the voltage of the battery hopefully later today

 

I've need heard of battery oil! I'll check it out

 

Did you have the battery disconnected long enough to reset the computer when you replaced it? Curious if you couldn't get it to go away with no battery connected for a few minutes.

 

Had the battery disconnected for a few hours, multiple times. It got rid of my CEL, but the battery light never went off

 

Something doesn't add up. If you don't own a multimeter, take your truck to an auto parts store that will check your battery strength and charging system for free. A good alternator should be putting out around 13.8 to 14.2 volts. You might have gotten a bad alternator. If the alternator was a cheap auto parts store replacement, they have been known to fail prematurely, a year or less.

 

Yes, I was meaning to make it down to the auto store to get it checked out today, but didn't make it. Will try tomorrow to make it down. Idid try the trick of pulling the battery while running to see if the truck died, but it held strong, even with everything that's powered on ( radio, windows, a/c). It is a cheap alternator in there right now, but I have been looking to source a low mileage Toyota alternator to replace it with.

 

Alternator passed at 14.2 @Timmah!

 

That's good. So you now know it's not your alternator. I'd check your grounds then. Make sure all your body grounds are tight and not corroded. Just follow the cables that split off the negative battery cable. There should be one ground that attaches to the driver side fender. I know there's another ground that attaches to the frame at the front of the truck below the grill and maybe behind the bumper. Just look around for any other grounds and make sure they look good.

 

That's done. I cleaned them all with baking soda and water, cleaned them all up and coated them with corrosion prevention.

 

Where did you get the alternator? I read on another forum that a guy had a similar issue like yours. His alternator tested fine, his battery tested fine and he checked all his connections they were good as well. He finally replaced the alternator and the problem went away. I read there's diodes in the alternator that can go bad and the alternator will test fine, but under a load, the alternator won't put out a sufficient charge. If I were you, I'd take the alternator back to the parts store you bought it from and get another one. Or better yet, visit your local junk yard or Pick and Pull and snag an OEM one off a wrecked 1st Gen Tacoma or 3rd Gen 4runner. If you go the Pick and Pull route, replace the brushes before you install it because worn brushes are one of the major reasons alternators fail to produce a sufficient charge.

Here's a video my buddy Sean and I made replacing the brushes on my alternator.

<iframe width="560" height="315" src="https://www.youtube.com/embed/71_kBhg6_-A" frameborder="0" allowfullscreen></iframe>

 

love watching your videos man, thanks for them!

 

Thanks John. Always stoked to hear people are being helped by our videos.

 

This alternator on it was from the junkyard, although not oem. But it was brand new. Just a temporary place holder until I can find an oem one. I'd be kinda surprised if both alternators were bad right off the getgo. The light never even flicked or anything when I switched them out.

 

Seems like your issue would be wiring or ecu now that you've replaced both the battery and the alt and given the ecu enough time to reset.

 

That's what I thought. I might try to replace the cables next. Otherwise I'll just unplug the dash light haha

 

ECU doesn't control the light I don't believe. It's all between the alternator's regulator wires and the cluster.

I was at the junkyard a week ago, and what looked like an almost brand new aftermarket alternator already had one bad diode in its rectifier, so looks don't mean anything.

Did you actually check the fuse with a meter? Sometimes fuses can look good and still be bad. Same with the wires. Best to check them with a meter.

 

I guess looking at a wiring diagram for this system would be helpful. I'd be interested to see how the light "knows" to turn on. If there's a fuse it would probably warrant replacing with a new one just to check.

@mechanicjon