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4runner over charging?

808 Views 7 Replies 4 Participants Last post by  The.Jesus
1999 4runner with 3.4l. The other day I went to leave for work and the battery light was on so I took my car. A few days later I started it and the light was off but came on shortly after so I changed the alternator. The light was still on but every now and then when driving around it'd shut off for an hour or so. I checked all the fuses and they looked fine so I bought a multimeter, when the light was on I was getting 15.3-18v. I ohmed out all the fuses and cleaned the grounds and added an extra battery to fender ground wire, I also cleaned the spots where the alternator mounts and i get low ohm readings from battery post to engine block, fender, and alternator case. I cleaned the “ea1” connector and the connector on the voltage regulator and still no fix. So i changed the alternator again. Now the light is out but its getting 16.6v when cold and 15.5v when warmed up. I checked my car to see if maybe my multimeter was off but no, my car had 12.3v off and 14.4v idling so I think the meter is accurate. Electrical stuff isnt my strong suit so I have no idea what to check next, any suggestions?
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Moving updates to comments.

Update: Despite having low resistance from the alternator case to the battery negative I added a wire going from the upper alternator attach bolt to the negative battery terminal and I’m now reading 14.8v.

update 2: on my way to work the battery light would come on for a second or two every so often. When the light was on the blower for the heater would ramp way up so I imagine its still over charging.

Note: bumps in the road and engine rpm have no corrolation to whether the light comes on or stays off.
Sounds like you are approaching this logically.

How old is the battery? You can see how much of a voltage drop you get when cranking. You didn't mention slow cranking so probably ok. Still good to know for troubleshooting. How are the battery cables and terminals? Do a voltage drop test across the cables. Plenty of youtube videos. I've had cables that looked perfect and were green and crusty inside.

The alt output is going to vary depending on the load the regulator senses on the system. Should be above battery voltage but not 16 -18 volts. Mid 14-15's typically.

Good luck with your troubleshooting and please follow up with whatever you find.
Battery is 2 years old, after sitting overnight it reads 12.8v, i have not had time to check voltage drop. I took the engine bay fuse block apart and I found some corrosion on the 12 pin connector in there but I cant find any information on the connector. Im looking to see what pin/wire goes to what. Any idea where i can find info on it?
Motor vehicle Electrical wiring Gas Cable Auto part
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This stuff works pretty good to clean contacts up. I'm told it's easy to find at music stores. https://www.amazon.com/gp/product/B00006LVEU/ref=ox_sc_saved_title_3?smid=ATVPDKIKX0DER&psc=1

You need to find the EWD for your truck. I bought a manual for a 99 4Runner for when I did my 3.4 swap but I'd have to figure out where I put it. I did the swap in 2013.
I found a website that has all the EWD but i cant find any info on that plug, I went ahead and cleaned it up but It hasnt been over charging since the other day so not sure if that is the fix. When it was overcharging it burnt out my headlight bulbs, almost left me stranded at work the other night. My plan now is to do the “big 3” wiring mod and continue monitoring it to see if it starts over charging again.
I had a problem similar to this after I did some work on my minivan. I'm not 100% sure which wire it was, but it wasn't the big one, it was one of the other two little signal wires that plug into the alternator. As I was reassembling the intake on my van (which has a transverse mounted V6) I managed to pinch one of those little wires in a bolt on the back of the intake, which was enough to mush the insulation enough to ground it out, resulting in the some sort of zero signal being sent to the alternator, so it thought it had to send back maximum charge (my windows REALLY sprang up and down like you'd want them to, all else considered.)
I'd pull that little bracket with the two wires out of the alternator, grab your multimeter, and see if you have a closed circuit over ground with either one of those... If you do, maybe check your wiring diagram to make sure that it's not supposed to go to ground, because I'm not a wiring expert. If not, then you may have found your fault.
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I have this same issue with my 22re, ever figure this out?
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