On my ‘87 SR5 Turbo.

i worked for about 3-hrs trying to get the horn to work. Hasn’t ever worked since I have owned it the past month.

Here’s what I know:
1) Contact plate inside the steering wheel seem fine and contact when pressed
2) I pushed the brass spring behind the steering wheel with a metal wrench and the horn Did Not go off
3) I have the original horn, a used Camry Horn, and a new horn off Amazon. None work so I had to be between the horn and the steering wheel brass spring
4) I followed the wiring from the horn and it looked damaged where the horn and Passenger Blinker wiring connect in front of the passenger wheel well. I rewired it but still no horn.
5) My MM shows power to the horn, so it’s the ground which is triggered by the contacts at the steering wheel and wiring from there on
6) 10amp fuse in engine bay fuse box is fine

Pics below. I cannot follow the wiring after the wheel well.

I did find a random connector not connected at the ground location near the engine bay fuse box, but looks like a different wire.

Any ideas? I literally gave up earlier by saying “who uses a horn these days anyway” but would like to get it to work.

 

Have you tested the Horn itself ??

I have replaced quite a few bad horns over the years .

I keep those and washer pumps sitting on the shelf

In all my problems never once did I ever need to pull the steering wheel

 

wyoming is fortunate in not having to pull the steering wheel. but he is correct about confirming that the horns do, in fact, work.

 

I do. I use it more than my brakes. Less wear on my truck - LOL!

Where on the horn do you see 12V?
The blue-Yellow wire (positive side of horn)?
The Green-Red wire (negative side of horn)?
Positive side may be different color on your model-year, but green-red IS negative side both on the 1986 (mine) and the 1988 (per schematic on FSM)

Correct. There is constant 12V on positive side. When negative side is connected to ground, horn sounds.
Please try connecting negative side of your horn to ground. Does it make a sound

Normally-functioning horn circuit is shown on my thread:
https://www.yotatech.com/forums/f116.../#post52381275

What do you see that is different from the "normally-functioning" description?

 

I hooked up a brand new horn from Amazon that takes two plugs (+ and Ground) and it didn’t work so I assume it isn’t the Horn. Also tried my OEM one and one off a Camry from the salvage yard.

 

Yes. I hooked the new Amazon horn to the positive side, then manually grounded it and the Horn worked. Which means the ground is the issue. Now what?

Ooh, and I think Green with White Stripe is + and Green with Red Stripe is Ground. The wires turn perpendicular inside the plug, so it’s hard to tell for sure.

 

Update: It works. I messed with the wiring and re-ran wires from connector to Amazon horn and it works for the first time. Horn sounds good too. I guess it was the wiring all along.

Thanks everyone for your help!

 

Awesome! Thanks for verifying wire colors. I updated picture on my post to show positive is green-white for 1986 to 1987.
Yes, Toyota components are bullet-proof. Issues often arise from poor wiring, assembly and/or maintenance.

 

glad you got it fixed...but was hoping to suggest my empty 22LR shell fix

 

I saw that - would have been nice if that was the problem! Very cool mod!