offset442

2000 tacoma v6 sr5, 70 amp denso (some jerk mechanic robbed the truck of the tow package 120 amp version at some point during shop service my work paid for took me years to notice, so it pays to just always do it yourself)

so work has been slow for me lately and my truck has been sitting idle for a few days at a time i have been having to jump start my truck after about 3 days i thought it was just a bad battery but i decided to key off load test the truck, i removed every fuse and disconnected all sorts of stuff but still had .35 amps of leaking load on the battery then i got the idea to disconnect the B+ charge terminal comming from the alternator to the main bus fuse and the leakage current droped back to the normal 60 ma that holds up volatile memory in the radio and ecu. As is .350 amps leads to a flat dead group 34 battery in about 6 days, needless to say this battery has been deeply discharged to irreversible damage due to this fault!!!

so the symptom is the alternator is draining the battery. i have another identical unit from my 98 parts 4runner and when tested its doing the same thing. Its not the alternator necessary it only leaks when the rest of the vehicle is hooked to the battery, ie if you disconnect the alternator B+ at the under hood fuse block but leave battery terminal connected you can measure 300 ma leaking between B+ and the positive battery terminal but if you disconnect the + battery lug and measure between B+ and the positive of the battery post their is no leakage current, then if you connect everything as normal and disconnect the engine harness from the alternator the leakage current stops so i think it has something to do with regulator control wires coming from the engine wiring harness causing the regulator to not shutdown.

on the regulator connector with the locking tab facing up there are 3 connections from left to right we will call them 123

1.
0.001 volts measured with respect to ground
11.3 ohms with respect to ground
0.008 volts when positively or negativity biased in diode test mode

2.
12.6 volts HOT (sense line?) also leaks an additional 40 ma when connected

3.
0.045 volts with respect to ground
0.008 volts diode test postive with respect to gound
0.856 volts negatively biased with respect to ground (output transistor from ecu?)
over 20 Mega ohms when tested for resistance to ground

ok so the problem is the regulator is not shutting down, now this is where i need help.................................

does anyone have any good information on how the regulator inputs work where they go and how they could have failed?

any ideas what could be causing the regulator to fail to shut down?

is this a common problem with the regulator interface? anyone care to load test theirs?

anyone think i just place a big fat iso-package schottky blocking diode in series with the B+ output?

any experience beyond swaping it out would be helpful

TheDurk

Do you have DRL's? If so, try this:

...pull the DRL main relay and see if the leakage continues...or if you know an easy way to disable the DRL's on your rig do that. I have heard of the DRL circuit causing this problem on a 4Runner with the same engine but I don't know the exact details. I do know that disabling the DRL's solved the problem for the guy that had it.

Here is the 4Runner circuit--you can see how it might happen.

offset442

i actually figured this out finally 30 mins ago worked on it all day too, i dont know how but here is the was the problem

there are 3 wires yellow, red, white or S IG L

so I noticed that IG was supposed to be ignition switched 12v but it was always hot, so i traced the wire back to a 7.5 amp fuse labeled alt-s or alternator sense.

Ok what the hell is the center red wire doing hooked up to the fuse for the yellow wire? ok so then i tuned the key on and the yellow wire goes hot, ok so the answer bcame obvious the red and yellow wires are reversed somewhere.

how the hell or where i don't know but im sure its my fault, i did a motor swap back in January and must have mucked something up. i seem to vaguely remember having to match wires from the charging/starting harness from the 4runner into my tacoma and having the color codes not match up, after i was done the alternator was charging and i never noticed the leakage current until it finally ruined the battery from excessive discharging

so i found a place and reversed, problem solved, leakage current gone, it only cost me a $120 battery to find out about it.

tantacoma

Interesting problem, glad you figured it out.

Thanx for posting the solution.

offset442

well, its worth noting that even as stock the plug is color code wrong compared to every diagram i looked it, the the yellow wire is supposed to be in the 3rd position as the warning lamp and the white is supposed to feed alt-s, so from the factory yellow was in the alt-s spot and white was in the lamp spot, you you can't trust the diagrams, you have to test the wire with an ohm meter with both key on and off, other wise its a hopeless also the alternator has the S IG L drawing on its label with the showing the locking tabs on the top with S IG L under them