You have one. It's a sub assembly in the dash that holds the gauges and lights.

 

YES! Another thing that could go wrong. Whoo Hoo!

 

Cool! yep, hoping for the best,. keep us posted.

 

Found this in another thread. This is why you need to be really careful about sharing around wiring diagrams

http://personal.utulsa.edu/~nathan-b.../6combinat.pdf
vs
https://www.dropbox.com/s/ue4hq1aeo0...combinat.pdf?m
vs
The diagram you had up there.

For the record, your voltages are slightly higher than I'd expect but not serious causes for concern. You didn't say where you're measuring them at, I assume battery but if not then you'll see slightly higher voltages (0.1 to 0.2V) at the alternator than the battery due to cable losses. The FSM guidelines for voltage are the standard guidelines for any flooded lead acid cell, and we shouldn't be cautioning people to replace their alts because of standard tolerance differences. In this case, I'd still suggest replacing the alt because the warning light circuit seems to be faulty.

This is a very modern voltage regulator IC:

http://www.freescale.com/files/analo...et/MC33099.pdf

Undervoltage detection is about 11V, overvoltage detection is 15.8V minimum. It will be considerably more advanced than anything from our vehicles. The set voltages for those are 14.6 and 14.8V btw, just for reference That's a standard charge voltage. Around 13.5 is more of a trickle charge voltage.

 

I would say that any electric/electronic circuit diagnosis should begin with a continuity test(measure resistance with an ohmmeter) to be sure the wiring or component you are checking is actually part of the circuit in question. There are many wiring diagrams for many models of Toyota trucks, I use them for a basic idea of the electrical circuitry, nothing more.
As far as my charge/e-brake light problem goes, installing a remanufactured alternator solved the problem. My old alternator was OK, but the integral voltage regulator was defective.
The key to the diagnosis of the problem was measuring the voltage at the 7.5A Charge fuse; it's supposed to be 12v, it wasn't even one volt. The voltage at the battery was also too high. The remanufactured unit I installed today came with test results of the unit. There is a "Voltage Set Point", which I assume is the point where the regulator curtails voltage to the battery, that is 14.8v. After this experience, I would say that if the voltage at the battery is over 14.8v, the voltage at the Charge fuse needs to be checked because the regulator is probably defective.
Also, I checked the voltage of the newly installed unit at the battery, it was a solid 14.5v. The defective unit was anywhere from 14v to 14.9v and jumping all over the place, in hindsight compared to the steady output of the new unit, that voltage fluctuation was another symptom of a bad regulator.
So, for about $70 the Toyota is back on the road. Thanks for helping me figure this problem out. Hopefully, this thread will be a help to people who search this problem in the future.

 

Glad to hear your problem is solved. Sounds like your regulator got a bit stressed, probably shorted the indicator transistor and caused the regulator to not work quite as well as it should have.

Where did you get your wiring schematic? I got mine from the NCTTora place before they got the takedown notice. It's for a 94/95 4Runner, and it seems to be the same for my pickup. For instance, I have a manual for a 93 PU that still shows the charge fuse, but that fuse is gone in my 94/95 runner manual and on my 95 PU. I hate it when they go changing simple stuff that should be the same for every vehicle!

 

The wiring diagrams are from Chiltons Manuals. One is model specific, 89-91, I believe, the other is from the 89-95 "one size fits all" version.
I used to have a 95 4Runner(the one in my avatar), the wiring was much different than the 90 pickup. I did notice while I was working on this alternator deal, that the diagram on the fuse panel door on the driver kick panel is not correct. Luckily, I never followed it, only replaced fuses with the same rating as the one that was blown.

 

My battery voltage with a new alternator is sitting at 13.3-.6 at the charge fuse I'm getting 3v is this enough to replace my external voyage regulator?

 

You have an external regulator, correct?
Meaning the output of the alternator winding goes into the input of the external regulator, correct?

Where are you measuring 13.6 - 13.6V?
At the output of the alternator winding?
OR at the output of the external regulator?

If you are getting 13.5V-15.1V at regulator output, then regulator is good.

IF regulator is good and IF you are getting 13.5V -15.1V at output of regulator, then charge fuse should have at least 12V on both sides of it.

IF regulator is good and you are getting 13.5V -15.1V at output of regulator, BUT charge fuse does not have 12V, then fault indicator circuit of the regulator is defective because it does not know that the regulator is good. In this case, your call whether you want to trust the regulator or not.

 

My 12.6 is at the battery posts yes external regulator and I will check at the regulator input output tommorow

 

First, I'm going to assume in your last post when you said 12.6V, you meant 13.6V. So as RAD said, your alternator is functioning.

But 3V at the charge fuse, you've got an issue there. Check both sides of the fuse just to rule out some defective connection. You should be able to put your multimeter probes right on top of the metal posts of the fuse, right through holes in the plastic.

Last, checking your regulator is fairly easy. You just need to check it over a range of RPMs from idle to 4/5k and test it under two load conditions. First is no accessories, and the other is basically everything you've got. Lights, wipers, radio, the works. If the voltage is stable on your multimeter at ~13.6V then your regulator is working fine.

 

12.V sounds like you may just be reading battery voltage. As mentioned above here's where you probe a blade fuse...

However without seeing what you have it;'s hard to visualize things.
It would help everybody understand what we're dealing with if you post pics of parts, schematic for you truck, what your measuring and where.. I only have one for 22RE with built-in regulator.

 

I was curious to know if you were able to get the problem fixed in your vehicle mine is having the same issue with the brake light and charge light.

 

1) Do all voltage checks I describe on my post how charging system works.
2) Monitor alt voltage and see what it is when charge fault light is on. IF it is between 13.5 and 15.1V when charge light is on, the fault detect system in alt could be bad. ALso have alt checked for ripple voltage..

 

I just finished swapping out my standard gauge cluster for an SR5 and both clusters have the charge/brake warning light ON. So I'll be checking my Charge fuse soon. Thanks RAD4Runner for the troubleshooting tips!

 

Most welcome, Tim. Make sure to do checks on all wires; IG, S, and Alt output B.
What matters more to charging system is the Engine fuse.
Charge fuse is merely part of the fault indication circuit. It should be called charge FAULT fuse. It does not enable the charging system. If you remove it fault light will go away, but problem is still there. If system is normal, removing the charge fuse will not affect function. Toyota mis-named many things.

 

time to do the voltage checks in my red '87. charge/brake lights are on after starting, and "battery" gauge indicates middle voltage. after higher rpm operation, charge/brake lights go off, and "battery" gauge indicates normal voltage at higher end of scale.

 

some numbers:
no warning lights on, ~14.2 V either side of charge fuse, and at battery
warning lights on, less than 1V either side of charge fuse, battery at 12.0V.

hit throttle for a bit, lights go off, voltage at batt and charge fuse jump to 14.2V.

indicates a no-charge fault, vs an overcharging fault. now to figure out why it isn't charging initially (sometimes), but once charging, it doesn't drop out back to no-charge while running.

 

Fault light indicating accurately.
Please check volts on IG wire.
Could also be brushes. I tried to check on my old alt but screws were roumded off.

 

i agree, it appears to be functioning correctly

i'll give that a whirl in a day or two...

could be the same for me - i assume the alt is original, and thus 35 years old