battery light

so i know that when a battery light comes on, it means the charging system is having some sort of problem. lately, if i let my truck sit for a day, as soon as i start it up the battery light comes on. no hesitation starting or anything, and no problems driving either. i had the battery and charging system tested 3 times at 3 different places. all 3 times, everythign checked out fine. not even close to having to say well these are a little low you may need to replace yadda yadda yadda.

so then after about 20 min or so of driving, the light goes out. this doesnt happen everyday, but it seems like it happens if i let the truck sit for a bout a day without running.

any ideas what could be tripping this light if everything is checking out ok?

2005 tacoma, 2.7, 70K miles, OE battery and alternator.

i know the battery is probably approaching the end of its life just due to age, not sure if thats contributing to the light or not.

 

ok so i downloaded the toyota repair manual to see what it says. it states"standard voltage is 12.5 to 12.9 at 68 degrees" for a battery not running.
mine is 12.85 and that was at 35 degrees

then for the alternator it states "run the vehcile at 2000 rpm with all of the accessories running. it says standard is13.2 to 14.8 for the voltage and 10A or less for the amperage"

well i dont have an ammeter, but my volts without a load was 14.09. i dont know how to test with a load. so is my battery light just dumb?

 

so i had a thought. i pulled the power wire from my battery for my amp on saturday. drove the truck all week, no battery light. last night after work, i reconnected the power lead for the amp. i checked to see if the amp was lit up or anything, and it wasnt. i didnt drive anywhere for the rest of the night, so i'd say the truck sat for a good 12 hours. i hopped in this morning, as soon as i fired up the truck the battery light came back on. and once again, as soon as i drove about 8 miles the light went off. also, i'd like to add i had the stereo off the whole time.

so i'm not sure if this is possible, maybe the amp is steadily drawing from the battery overnight, and in the morning the battery is low but strong enough to crank the truck. but its so low that the alternator can't put the out put to recharge it and triggers the battery light? thats the only thing i can think of, any thoughts?

here is my stereo set up, its nothing huge. i have the stock radio, a line ouput converter that feeds signal to a kicker amp (i forget the exact model, roughly 120 watts rms), that goes to 2 6.5 speakers and a 8" subwoofer. certainly nothing that a stock alternator couldnt keep up with. i've had 800 watt rms amps hooked up to stock alternators before with no problem.

so sorry for my lonnnnng read. any help is appreciated, in the meantime i will re disconnect my power wire to my amp.

 

does that sound feasible though? its drawing the battery low enough that the amp can't charge it fast enough therefore triggering the light? i have a feeling the amp isnt shutting off maybe due to the fact i'm using the factory radio and maybe spliced the wrong wire for the remote turn on

 

i just went out and checked at work, as soon as i start the truck the amp turns on whether the radio is on or not. so looks like when it gets warm i'll be tearing out the radio and checking to make sure i splice it in the correct wire.

 

jsut as an update, with my fog lights and stereo disconnected the light still comes on so that wasnt what was causing it. i'm still lost on this one...

 

It seems you have eliminated the amp as a problem source, but for others with a remote turn-on issue I would recommend a product by David Navone that does remote turn on and line out conversion - the N-RHL2 for like $25.

BTW, O/T, but...Navone and Richard Clark made quite a name for themselves in the car audio world when they once tried to enter a sound off competiton with a custom woofer of their design...pic below

 

well i pulled the alternator off the truck today, apparently it tests fine in the vehicle but outside the vehicle it fails the tests. so i ordered a new alternator today. kinda disappointed...70K and the alternator is done? thats pretty bad...

 

its a mechanical part bro...things fail

 

true, i've just never had one fail as early as this one. things happen

 

If it's the alternator, you may be able to rebuid it. I replaced the brushes on an odl Corrola once and it worked for another 50k mi.

 

yeah i talked to a place that rebuilds them. i explained how my light intermittently comes on and goes off. he said it sounds like it could be a diode on its way out, or something else starting to fail. he said they would have to tear it down to see exactly what was wrong with it, order the parts etc... he said i'd be looking at 2-3 days down time and upt to $220. i cant have my truck sitting for 3 days, so i found a rebuilt one from autozone with a lifetime warranty for $169.00

 

I am having the same problem with the battery light coming on when starting, I have no added features to worry about. I have a 2007 Toyota Tacoma I have replaced the battery and the light still comes on, Could you tell me if when you replaced your alternator if that has fixed your problem. Thank You

 

Welcome to TW.

Three year old thread revival... I would guess lack of repost means problem solved.

 

Yes, the alternator fixed the issue. And earlier this year the rebuilt failed. Love lifetime warranties

 

How long is a life time alternator wise

 

Considering I can pick up the the parts at a bearings and more farm parts store in Minnesota for 7-15 bucks id say it would be wise beyond the vehicles life... Unless maybe the alternator was for a tacoma

 

My 2006 Tacoma battery light intermittently came on and off, the battery and alternator tested good. There are three wires that come off the plug in of the alternator. I unwrapped the wire harness and found the white wire had corroded on the inside of the wire and it broke in the middle. I cut out 3” out of the wire to eliminate the corrosion. Spliced, soldered, and heat shrinked in a new piece of wire. Light is now off and truck works like it should.

 

I'm having the same issues with my 2008 Tacoma. I replaced the alternator less than a year ago. Just recently the battery light started coming on for short and long periods of time, then go off. Doesn't matter if every electrical item is on or off. At times, the fan speed changes and the lights occasionally get dim, then normal, then dim ect....
There doesn't seem to be a pattern when the battery light illuminates.
And the truck cranks like a champ everytime.
Today I had Auto Zone to check system and the tester showed my 1 yr old battery was bad, even swap on a new battery and several hours with just a few miles later and the light is coming on, but going out quicker than before.
I've checked the ground from the truck body and also from the motor block and both read the same and the voltage meter shows a steady charge from the alternator.
Think the ground lead to the frame could be an issue, or just a defective alternator?