1999 4Runner Battery Light - Alternator?

[Ty4Runner]

Hey guys! New to the forum and have a maddening problem.

My battery light started coming on a few weeks ago. I thought the batt was ok so I pulled the alternator and took it in to have it tested, at NAPA, to make sure it was ok. Tested fine, so figured it was the battery. Replaced the batt and all was good for 2 weeks. Light came back on and so I pulled the alternator again, took to different place (Advanced Auto Parts), and it tested fine. There happened to be a Toyota tech there buying some stuff, and he said he thought it was the ribbed belt, or the cable from alt to the batt.

I checked the belt, it wasn't shiny between the ribs, so I retightened it slightly, and all was fine..........for a week!

The battery light came back on Monday (Labor Day), so I parked it where I work and drove a company truck home, and decided to change the cable from the alternator to the battery on Tuesday morning.

Well, that cable must do something other than run to the battery, because when I completely unhooked it, and ran the new one I had nothing. So then I reattached the old cable ends, and added the new cable. So now I have two cables from the alternator to the battery.

I drove home and everything was great. Started to work this morning, all was well, stopped for gas, and when I restarted the truck to finish my drive to work.....THE BATTERY LIGHT WAS BACK ON AGAIN!!!

So, we've got a repair place in town that about all they do is rebuild auto alternators and motors. They say the brushes wearing out will cause that type of intermittent behavior, and that if it was the voltage regulator, it would just quit.

Has anyone else had a similar experience? Did you resolve your issue? I'm just really gun shy about throwing more money at this problem.

Thanks in advance!

 

[Uneek]

Moved to 3rd gen sub forum.

 

[CommanderDave]

I am doing some research on a similar problem. I note that this post is several years old. Did you have resolution?

My sequence of failure: (2001 Limited 4wd)
-charge light comes on. Batt is only a year old, and alt is factory original, so no brainer...replace alt.

- 2 months later, light comes on again...then goes out. Intermittent failures persist for 2 weeks. Finally get a 'failure' when I can pull over and put multimeter on. Voltage across battery poles with engine running confirmed at just over 12v.

- Replaced alt, and cursed the person who rebuilt it.

- 3 months later, alt light again! When light is off, charge 14+v across the battery. When light comes on...just over 12v. Swapped batteries with a known good battery. Condition persists.

- Today...decided to play with it some more. Start engine. alt light on. 12+v at battery. Moved positive probe to output leg of alt. 15+v!!!!! Opened fuse block under hood. Positive lead on hot supply to fuse block. 15+v!!!! Moved negative probe to body ground, and same.

Anybody have some clues? The alternator is producing power, but is only intermittently getting that power to the battery.

Where should I start?

 

[snivilous]

I am doing some research on a similar problem. I note that this post is several years old. Did you have resolution?

My sequence of failure: (2001 Limited 4wd)
-charge light comes on. Batt is only a year old, and alt is factory original, so no brainer...replace alt.

- 2 months later, light comes on again...then goes out. Intermittent failures persist for 2 weeks. Finally get a 'failure' when I can pull over and put multimeter on. Voltage across battery poles with engine running confirmed at just over 12v.

- Replaced alt, and cursed the person who rebuilt it.

- 3 months later, alt light again! When light is off, charge 14+v across the battery. When light comes on...just over 12v. Swapped batteries with a known good battery. Condition persists.

- Today...decided to play with it some more. Start engine. alt light on. 12+v at battery. Moved positive probe to output leg of alt. 15+v!!!!! Opened fuse block under hood. Positive lead on hot supply to fuse block. 15+v!!!! Moved negative probe to body ground, and same.

Anybody have some clues? The alternator is producing power, but is only intermittently getting that power to the battery.

Where should I start?

You need to play with your multimeter more and stop replacing everything over and over. Autozone has some good wiring diagrams online, pull one and go through everything with a multimeter. Here are two issues I had recently that are similar, and might be able to lead you in the right direction:

First problem a few weeks ago I had, turned out the plug on the bottom of the engine bay fuse box wasn't transmitting full power. One side had full voltage, somehow the other side had like 3V, so whenever I would hit a bump the plug would get jiggled and sometimes turn the alternator off and stop charging the battery.

Another issue I've had is the alternator fuse being blown (or partially), but not visually, only way to tell was to check continuity.

 

[RunnerandGunner]

Make sure to inspect the plug in the rear of the alternator. My battery light came on a couple months ago, I inspected the alternator and found the power wire completely corroded and one of the terminals on the back of the alt corroded off and stuck in the plug. I have a parts truck and it was the same thing. Same terminal corroded off, it was still in the plug so it was making contact intermittently which made the light flicker. I replaced the alt and the connector and now no more problems.

 

[CommanderDave]

All,
Researching a new issue, and note that I have failed to update the resolution on my issue.

Intermittent issue came to a head when I jumped in one day, turned the key, and the vehicle had no power. Using schematic and voltmeter, I traced the issue to be between the main fuse block (under hood), and the key switch...suspecting issue to be in fuse block.

A more competent electrical diagnosis person than me was called onto the problem. They quickly found the ALT fuse to have been arcing on one of the legs, and finally enough copper was melted away that it failed altogether (fuse never blew, and showed no signs of damage from the top).

Now, for how this failure set up, we have to go back in time a full year and a half before failure. I was jumping someone off, and in my haste (and yes, I find this a bit embarrassing to admit) I crossed poles with the jumper cables, and blew the ALT fuse. It was raining, and I am weak on electrical. When I couldn't get the fuse out, I had it towed to a mechanic that I used for things I perceived to be a bit over my skill level. Turns out, the legs of the ALT fuse bolt in, and you have to gain access to the bottom of the fuse block to make the fuse change. Mechanic fixes problem, I pay him for his expertise, and life moves on.

Now, back to the failure. Turns out, the fuse had not been installed properly 1 1/2 years prior. The fuse was forced in, and was not aligned properly. One of the legs was pushed into the body of the fuse (though it still didn't look bad from the top). The legs were not bolted back in, but held in by friction. Sufficient contact was made initially, but as the legs worked loose, they would arc. This is when my intermittent alternator problem showed up. After the second alternator, I realized that was not my root cause failure, and finally, the fuse made not contact, and the vehicle was dead.

The repair involved shaving some melted plastic out of the way, so that a new fuse could be installed. This has held nicely, and if it does become a problem, the fuse block will most likely need replacing. I hope it holds, because that is one MESS of wires!

 

[Trapperpete52]

Thanks for update

Even though an older post gives me a starting point.