BradsYota

After reading threads to no avail, I've started my own.

The Problem: My battery is not charging.

Details: The charge light and brake light are illuminated on my dash. At the G2 junction on the included (1988)wiring diagram, I get a reading of ~16v(new alternator). When I put the multimeter to the battery, I only get the voltage of the battery-no charging/alternator output voltage. At the entry point to the fuse block, I get the battery voltage reading. This problem began after washing my engine bay. I've included images of my findings.

What I've tried thus far: Replaced the alternator, replaced the battery, and visually inspected the fuses.

Question: What should I try, how else can I isolate the problem?

Wiring for I believe a 1987 Toyota Pickup


Charge light and brake light on the dash

The (New) battery and its voltage with the car running

The voltage reading at the G2 connection. This is coming from the alternator

Reading at the charge fuse right side

Reading at the charge fuse left side

Charge fuse out - left side

Charge fuse out - right side

2ToyGuy

I would pull the heavy wire from the alternator going to the battery, and fuse box, Terminal B I believe it is, off at both ends and ohm it. Pull both leads off the battery before doing anything. It takes very little external voltage to destroy the ohm part of a meter.
You'll need to pull the top part of the fuse box up to get to the battery end of the wire, IIRC. It bolts to the heavy duty fusible links in the fuse box. The 80, 40, 30 Amp ones there in the fuse box. The wire from the battery positive bolts in there as well. Ohm that wire out as well. Lastly, make sure that where these wires bolt down is clean, and free of corrosion. A small amount of corrosion can cause big problems.
Also, make sure the plug going into the back of the alternator is seated properly. I've had troubles like this if I don't make darn sure that plug is clean, and seated properly. Once I started using a little dab of silicone dielectric grease inside the plug not only was it easier to make sure it was seated down properly, but it kept all the gunk out. Made a huge difference.

Good luck!
Pat☺

RAD4Runner

Did you read this thread?:
https://www.yotatech.com/forums/f116.../#post52401963

15.96V, assuming your meter is accurate, is overcharging. (see above link)
Readings at charge fuse are as expected. "L" (fault) signal from alternator is pulling it low to ground negative side of charge and brake fault bulbs

My educated guess is:
1) There is break in "B" wire between the "G2" and battery positive.
2) Thin wire "S" input into alternator taps off that segment of thick "B" wire.
3) Because "S" does not see that voltage, alt needs to bump up alt output, causing overcharging.