Question about 2003 Toyota 4Runner

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IG wire that plugs into alt.

I need to tap the IG wire going to the alt. to a post on a dual battery isolater. The little wiring diagram on the alt. is confusing. To be sure I need the color of the wire.

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  • sandiegohefn Sep 04, 2008

    Thanks for the quick response !!!!!!!!!!



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On your 4RUNNER 03.
The IG wire colour is: YELLOW and RED.
On the Alternator connector.

I hope this help on your question.
Thank you for use fixya..

Posted on Sep 03, 2008


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1999 Toyota Avalon battery discharge light and abs light intermittent. Changed battery and alternator no change to issue. Checked voltages with multimeter 12.73 with car off and 17.03 with car on. Ple

17v on is bad. its too high.
are you using a good voltmeter. a DMM, ? or relic analog meter.?
you put a new alternator in the car? not from autozoned i hope.
the wiring to the Alternator must be all good, them includes the case ground and battery cables, end to end, good and tight and not corroded.
the regulator is inside your ALT>
the ALT has 5 connections 1 is ground. any bad, reg can go nuts.
newer cars , go less nuts. they detect more errors and shut down
your is overcharging and will burn a battery up in no time.(heat)
Grounds good.
idiot lamp ,must be there, an working or alt may start up dead.
the lamp creates excitation currents, to boot up ALT.
wire B, goes to battery via fuse link, if this big wire fails. all bets off.
wire IG goes to 7.5A gage fuse, it must not be blown.
wire S, (sense) is 5amp ALT-s fuse, this senses battery voltage
if this wire drops in voltage the ALT will go to max. (or shut down)
toss coin there, lots of regs sub'd out in so many years, and rebuilts.

the regulator is not working right.
that means 3 things.
1: reg is bad.
2: reg is being lied to. (bad wires) even bad battery.

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1 Answer

Battery light alternator

The Charge lamp comes on with the Alternator fails to keep battery charge going. (lots of way to fail, and ALT Is 100% good) it's a system. each part of it must be good, end to end.
i put my voltmeter across battery, i start car, i see 13.3 to 15vdc, alt is good.
no? , i see now, 12.2v. ALt is dead, (i didnt say bad) and battery is sightly discharged, 12.6v is charged. (key off, rested voltage)
This 12v tells me the ALT is shut down. only why is the question.

how can any charge system fail,
bad battery tops the list here, they LOVE to fail.
1: belt slips.
2: belt missing
3: bad alt.
4: bad wires to ALT . (corrosion on any wire or lug)
5: fuses blown , any listed below.:
your alt is not an ECU controlled, alt ,its 100% self contained

did you ever remove the ALT and blow the 100 amp fuseable link
the first step of any alt pul, is the pull the NEG, battery lug or BOOM.

im logged in to so can you.

and what do i see.
a 5 wire ALT. one is the frame ground, so it must not be rusty or..... it fails. frame to engine block. no rust here.

wire L , yellow.goes to dash LEDs (alt failure idiot lamps) (this works)
wire. S white goes to ALT 5a fuse, is it blown?
wire :B B/G color, goes to the 100 amp link fuse. (blown>?)
wire IG Red-white, goes to a fuse marked 10A gauge.

i think the IG wire is the voltage sense wire.
no sense, no charge. I think the whole I/P dash cluster goes dead when this fuse blows.

The S wire is the boot strap voltage sense, it wakes up the regulator .
if open , the reg stays asleep, as does ALT.
Alternators can not self start, the regulator has boot strap device
that cures that. called self excitation. so this wire is critical.
All wires except the L wire is critical. in this case.

the B wire is the big wire, it charges the battery . 50amps or more..

any of the 5 paths open , kills the ALT dead.
The REG inside the ALT can also shut it down.
eg: battery bad, with huge cell resistances. total.
eg: overvoltge for any reasons. including attempts top run car with no battery, (dont ask)
eg: over current (battery cells 1 to 6 shorted) or 25 KC lamps added.
eg: over temperature shut down.

that is about it.

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1 Answer

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Bolt new alt. on bracket
Plug wires back in
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I need the wiring diagram. I'am doing rewire on a 66 Chevy truck to a one wire hook up. I have anew pigtail plug with the excitor wire anda short wire lable alt barttery with a1/4 lug on it. Do you puy...

The red wire goes to the lug on the back of the alternator (B+ connection) You need to run another wire from that terminal directly to the battery. Normally, the remainder of your power accessories will be attached to the starter main terminal but you could run that from the battery as well since that's the other end of the same wire. I wouldn't use the alternator terminal for that only because the insulator on the terminal could overheat and melt if overloaded for any reason. In any case, everything except the wire between the battery and alternator should pass through the ignition switch so it's all off when the key is off.

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My software won't let me link the diagram to the internet. So I will describe it to you. I'll use factory
color codes, so if you have any harness left you can
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The (F) orng/ltblue wire go's to the field terminal on
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The most common and popular model.
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The existing regulator should have the connections marked.
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