maxvp01

Hi I have been chasing this no brake light problem for about 3 weeks now.. No luck at all. This is a 1989 toyota pickup 3vze, 5 speed 4wd.

Some history of the truck:

I bought this truck last year for $60 and rebuilt engine and transmission and replaced entire fuel system. For all I know the brake lights might have never worked. All my other lights and signals work.

So I read some forums and tried all the simple things first, changed bulbs, bent the fuse to make better contact, tested brake light switch (tested out good).

I have checked the trailer wire harness. Looked like the previous owner scotch locked them and wrapped them in duct tape. I unwrapped them and inspected under scotch locks, no corrosion or breaks.

Next I checked to make sure power is going through fuse, to the input wire (green/red) of the brake light switch, 12V.

The output wire of the brake light switch is (green/white) and I traced that whole wire behind the dash (cut the whole harness open to thoroughly inspect it), down the A pillar, to the connector under the passenger seat, no nicks or breaks anywhere, and it has continuity throughout it.

This next part is the confusing part. I’ve never seen anything like this before:

I have a fish finder with a 12V battery I sometimes use as a poor mans power probe. I hooked the positive from it to the output wire of the brake light switch (Green/White) and the ground to the sheet metal that mounts the radio. The brake lights are lighting up.

Naturally I think it would mean there is a bad ground. So I run an external ground wire from the negative post of the battery to the same location of the radio sheet metal. I first try with the brake light switch hooked up- brake lights don’t work. Next I unplug the brake light switch and jump the wires together (with the external ground still hooked up) and there is no difference, the brake lights still don’t work.

So now I leave the external ground I made and make an external power wire from the positive post of the battery to the output of the brake light switch and the brake lights still do not work.

I am so lost. My neighbor thinks I should just run a fuse tap and a new wire to the input of the brake light switch, and see if that works.

Why would my fish finder 12V battery cause the brake lights to work and me running wires directly to my truck battery not even make a difference?

Any help is much appreciated

RAD4Runner

But did you check if you were getting voltage to all the points you say you have continuity to?All the way to the brake light connector and receptacle?

Keep it simple. Poor man's power probe is $7 multi-meter from Harbor Freight that many of us have. Never take your truck where it's designed to go without a multi-meter. Next to our senses... see signature

maxvp01

So I started voltage dropping like you said, with one lead on the green/white wire pin on the connector, other on a known good ground i get 1.3V. Next I move to the brake switch connector and get 1.3V on both sides..

Next point I need to take off fuse block but i’m not exactly sure how that comes off.. I unbolted the bottom bolt and it’s held on by something on the top. Plastic clip maybe?

Any way to get it off without damaging it?

maxvp01

The picture might speak for itself.. But I found the problem. Not only are the pins spread out, it’s been melted around the area. Those fuse blocks are a pain in the a** to remove even with no interior in the truck.

RAD4Runner

Nice! There you go. Patience and methodical troubleshooting, and like I say in my signature, our senses are our best tools - this time senses of sight and feel
There's melting because when connections come lose, they get hotter than normal - like when your flatiron plug is loose in the wall socket.
You should be able to clean and tighten those. Maybe with a thin strip of fine sand paper, contact cleaner,then bend them back.
Somehow your fuse block looks different from my 1986

maxvp01

That’s interesting to know! It’s possible they changed the fuse block design between body styles.

But as for the fuse block i’m going to run down to the junkyard and grab one. We got a classic toyota junkyard nearby with only 4runners and pickups and he has reasonable prices. Don’t know if i’ll have the patience to do what you described haha.

Thanks for your help!