I was having battery/charging issues roughly 1 month ago. Car would begin to buck, miss, and hesitate when driving longer than 15-20 minutes. The tach would also begin to jump around erratically. Checked the battery and found that the voltage was dropping seriously low. So, my first inclination is the alternator/charging system, or a short somewhere that is drawing voltage. I cleaned up the fuse connections going to my amp and reconfirmed that all my alarm/bluetooth/etc connections under the dash were fine and tight. Additionally, I load tested the alternator and did not see any signs that the problem was the alternator.

It appeared that my cleanup of the fuse connections (there were some strands of wire that had worked loose and I theorized that this could have caused some arcing resulting in voltage drops) had worked. All was good for about 1-2 weeks. Even made the hour drive to the NELOC Ross Dock meet without a single issue.

Well, the problem resurfaced last week eventually leaving me stranded and having to tow the car home. I resigned to the fact that the alternator must be the culprit and I swapped that out for a reman unit from Thul's. Install went smooth and all seemed to be fine initially. After about 15 minutes we noticed that the discharge warning light was on. (I can't say if it came on immediately after the install as I did not check nor remember seeing it upon starting the car). I checked the battery with my multimeter and saw that the voltage was "cycling". example: Car idling with the only load being headlights. Voltage would rapidly drop from 13.5v to 12.5 volts. Then the alternator would "engage" (you can hear a load being placed on the engine) and the volts would rapidly rise back to the 13v range. Over some time though the peak voltage would be .1-.2 lower than the previous cycle and the lowest voltage would continue to get lower with each cycle. Effectively draining the battery.

I have tested the system for amperage draw with the meter in series with the battery and found nothing out of the ordinary (.07mA).

I tried a test drive last evening as well and the car dies completely. Once it was jumped it would maintain drivability for about 5 minutes and then the voltage would rapidly drop, causing everything to dim. Suddenly, a wave of voltage would come online and everything would be back. But only for a short time as everything would dim again, eventually leading to complete failure of the battery and a dead car again.

Wondering if anyone has experienced anything like this and what their solutions were.

I am currently removing the new alternator to inspect all connections and inspect all wiring leading from the alternator.

Also, If anyone happens to have info on the 3 wire plug to the alternator it would be appreciated. From what I understand, 1 or possibly 2 of the wires recieve an ignition signal (voltage) directly from the ignition switch and that the 3rd wire is what feeds the discharge warning light. Can anyone confirm this and let me know which wire within the 3 wire harness is which??

 

#14 and #15 C12 charging and warning light combo meter. Right in the middle of the schematic.

*poof*

 

Thanks Brian!!

Any thoughts on this below?

I see that an ignition signal comes from the ignition switch through the charge warning light combo meter and down to the regulator of the alternator. I also see that the Trac Control ECU is tied to this line. When the problem first began to surface I noticed that my TRAC light (which has been fluctuating between on and off alot lately) seems to flicker and dim before anything else. WHat do you think the possibilities are of the TRAC ECU going bad and causing a short/voltage drop?

 

I've eliminated the TRAC ECU as a problem by disconnecting the ECU. No change.

 

Give these 2 some attention.

 

Alternator sensing fuse is OK. Inspected and fine. I also swapped out for a new fuse to be safe and no change.

Pretty much pitch dark here now and I don't have a garage to work in so that will most likely be all for tonight. Just some further research.

Why do you suspect the starter relay as well?

I will look at it though, as well as the main ignition relay. The discharge problem definately gets worse as the car heats up. I'm thinking that a relay is a potential suspect here. Perhaps a N.O. relay is "locking" open for some reason and not allowing an ignition signal to get to the regulator.

 

Yeah Ive been having this problem for a month now.. Its horrible. Im trying to get the Toyota Tpat instructors at my school to actually take a look at my car, but they have been real busy this week... I know how you feel, replacing EVERYTHING and still having the same problem. I've been through different alternators, batteries, +battery cable, multiple grounds, tried taking various fuses out to try isolating the problem and still came out empty handed. No information on Alldata about a problem like this, no TSBs or recalls. Nothing on Mitchell online.

If I do find information on what may be causing this, I will surely post up the cure for this.

 

Well, the new OEM Denso alternator solved the issue. A local friend and Toyota mechanic, who is also the owner of a LS400, recommended the factory unit. He said that he tried two different aftermarket units and neither worked.

I put my Denso unit in yesterday and all is good now.

 

Yeah I was going to try an oem one next.. Until I find out that my wheels have been stolen and they are sitting on wood logs in the UTI parking lot right outside the toyota building.... So I guess I have more things to worry about than the car not moving now =[

 

Man that sucks!!!! Sorry to hear that!

May the thieves spend an eternity being anally raped by a Hippo!