BATTERY LIGHT WON'T TURN OFF!

Hey Tacoma Peeps,

So, I've changed my battery and checked my tranny and my damn Battery Light won't go off. I've driven the truck for almost a year now with the light on and never has it been a problem for me. Has anyone has this problem? Does anyone know how to reset the light or to check if the chip for the Battery light is malfunction? HELP!

 

Has your alternator been checked?

 

Yes, I meant to say that rather than tranny!

 

Electrical short somewhere

 

Right, can the average joe track that down or is that a job for a pro?

 

We'll depends on how mechanically inclined you are. Me personally I'd get a free diagnostic done from somewhere and do the work myself cuz finding electrical gremlins sucks ass

 

I had that problem. On mine I found the wire from the alternator that send voltage info was loose. Some research Led me to this site, http://www.bodenzord.com/archives where he explains that wire, where it is and what it does. I found it and it was damaged. Fixed it and the light went away!

 

Right, think I will try that route first and see what happens!

 

Tiger541, tried the link you sent me and it send Error 405, link not found, can you try again? Thanks!

 

Check all the connections from the alternator to the battery and the grounds. Make sure they they are clean and tight.

 

Bodenzord.com
Find the Tacoma section and then his big 3 upgrade article. Very informative and detailed

 

http://www.bodenzord.com/archives/477

Pay attention to the little note on the bottom left corner of the schematic, as it tells you what wires are for what engine

 

Wow, that was helpful, thank you everyone for your help! I'll keep you all posted on the outcome.

 

I just went thru this today with my son's 98 Tacoma Prerunner with 2.7L. Battery light came on this morning after flickering for a couple days then his truck stalled. Had battery replaced under warranty started right up but battery light was still on. Then when he got home we took truck to get alternator tested and they said new battery was down to 60% charge and we had to remove alternator to test. We removed it and had Alternator tested at Autozone and they said it was good. We checked fuse Alt-s and it was good, all connections were good. Battery voltage was 12.4v So we replaced Alternator. Immediately battery light went off and battery voltage went up to 13.68...Possibly alternator test good when cold, not sure. But problem is fixed with new Alternator. Good luck

 

Put a meter on the battery and start it. If the voltage does not go up, it's the alternator.

 

Mine also won’t turn off new battery and alternator and is always on. It has been on for two alternators now

 

This is the alternator bible, with the failure mode section giving possible causes for an alternator failure.
http://www.billavista.com/tech/Articles/Alternator_Bible/index.html#failure

So what can go wrong with an alternator? Fortunately, not very much, as they are pretty simple and rugged devices. However, they do operate in a pretty harsh environment, are subject to a lot of heat, and don't last forever. This is a list of some of the most common things that can go wrong.

1) Wiring

Often a problem that seems like it might be the alternator isn't the alternator at all. Fortunately, there aren't a whole lot of wires to go wrong, but they should always be your first check. Make sure all connections are clean and tight; make sure that there are no short circuits or open circuits in the wiring (never run an alternator with the output terminal in an open-circuit condition, by the way); and make sure the wires are not crimped, pinched, frayed, tight, or otherwise in distress. Also make sure the connections between the alternator case, mounting brackets, and engine block/head are clean, corrosion free, and tight. Don't forget to check fuses, circuit breakers, and fuseable links!

2) Belt

Another major culprit is also not the alternator, but the drive belt. Make sure it is clean, not worn or frayed, free from glaze, appropriately tensioned and not slipping, jumping, or jamming, particularly at high engine rpm. Check to make sure there is sufficient engagement between the belt and pulleys and modify belt routing / pulley arrangement as required.

3) Bearings

As we know, the rotor spins at very high rpm within the case, and is supported by at least two bearings - normally sealed needle bearings. Heat, time, and harsh conditions such as mud, water, and dust will eventually bring the bearings to the end of their useful service life. This will most often show up as a grinding or squealing noise. To make sure that the noise is in fact the alternator bearings (and not some other bearing like an idler pulley), disconnect the alternator drive belt and turn the alternator pulley by hand listening for any noise and feeling for any roughness or harshness. Also check for endplay and sideplay in the pulley. Be aware that it is also possible for the bearings to seem OK by hand, but to be noisy when subjected to the load of the drive belt, so watch out for that. Fortunately most alternator bearings are available separately or in rebuild kits and they are fairly easy to R&R.

4) Windings.

The windings take a real electro-magnetic beating. Over time they can break down, short out, or open-circuit. The stator windings are most often the culprit with bad windings. Because each of the three phases in the stator has its own separate windings it is possible for the alternator to still operate, albeit at much reduced output, with one or even two sets of bad windings. This may be the case if it operates but output is low. Of course, if the rotor windings are bad, the alternator will not operate.

5) The Electrical Bits Inside

The other internal parts are also subject to wear, thermal breakdown, and have a finite life.

Chief culprits include the brushes, the voltage regulator, and especially the rectifier. Over time and with use, the diodes in the rectifier weaken and don't work as efficiently as they used to - especially when hot. Eventually they can stop working altogether. One possible tell-tale sign of a rectifier on the way out is an alternator that works well when cold, but whose output weakens as it gets hotter and/or electrical demands increase.

Troubleshooting
Sadly, these days we live in a discard-and-replace world. Nobody fixes anything anymore. Cheap offshore manufacturing has just made it cheaper and much more convenient to junk a suspected bad part and replace it. To be honest - this isn't always a bad thing - the availability and reasonable price of remanufactures alternators make this a pretty valid option - IF you are sure the alternator is bad. The possible exception may be the SI-series alternators that are very rebuild friendly.

Of course, we should probably still be able to do a little troubleshooting, as often times an electrical or charging system problems shows up and we are not sure whether it is the battery, alternator, starter motor, solenoids, wiring, relays, fuses, etc. etc.

Following is one approach to help narrow down whether the alternator is bad:

Eliminate the simple/obvious/unrelated

1. Check the belts and wiring.
   
   
2. Check that the battery is in good condition and has a good charge. It is damn near impossible to do any reliable electrical troubleshooting with a bad battery installed. Check the voltage across the battery terminals with the engine off. If voltage is:
   
   
   • > 12.6 – Battery is good
     
     
   • >11.9 & < 12.6 – Battery needs to be charged before proceeding
     
     
   • <11.9 – Battery is no good. You can try and bring it back to life and charge it, but especially if it has fallen below about 10 volts, it is probably toast.
     
3. Check that the source of your trouble isn't something dumb like lights or radio left on.

 

This. I had the same problem on my 2004 SR5. The small white wire from the fuse box to the alternator plug was chafed and broken clean through up inside the wire loom.