N70 Horn cabling diagram

[Jex]

Can anyone tell me where I can get a circuit diagram for the horn circuit on a 2006 lux. The spiral cable in the steering wheel has just been replaced on a recall after many years of not working. Now the single wire horn plug behind the grill has +12v in normal state & the +12v goes when the horn button is pressed. Very strange ? Is this normal ?

[Tony Prodigy]

If you have +12v at the horn, then technically the horn should be sounding regardless. If your horn button is NOT pressed, but you have +12v at the horn, then it looks like your horn relay contacts are welded or stuck in the normally closed position. 

Remove the horn relay and see if you still have +12v. 

Your horn could be faulty too. 

[Jex]

There is +12v at the horn at all times until the horn button is pressed then it goes away ? Yes, when I reconnected to the plug it went continuously until the button was pressed. This is how I got it back from the Toyota dealer after they replaced the cable in the steering wheel. They didn't indicate to me anything was not working properly. I would like a circuit diagram to see how it is actually cabled.

[Tony Prodigy]

So the horn stays on continuously when the single wire is hooked to the horn and when you "press" the horn button it stops the horn ? 

So what Toyota did was leave the wire unplugged on the horn ? Otherwise the horn will be blaring all the time right ? 

[Tony Prodigy]

It's possible they hooked the power wire to a ground which is why the circuit is complete without touching the horn button. It makes sense when you press the horn button the circuit breaks. It's like the switch is in bypass.

I suspect that wiring loom they replaced is probably not for the vehicle it was intended for. The horn circuit is quite simple actually. 

You should ONLY have +12v at the horn after the button is pressed as the power signal is sent to the relay, which energises the relay closing the normally open contacts. Toyota must have put an apprentice on this one and was too embarrassed to own it.

Go to page 222 on this pdf. It may not be for your exact model, but it's a good summation of how any car horn circuit is wired.

http://www.tuningconcepts.com/Cars/Hilux/VigoElecWiringDiagram.pdf

 

Edited September 16, 2021 by Tony Prodigy

[Jex]

Thanks mate, yes I'm convinced they have stuffed up, I have called them and taking it back tomorrow to check again. They only replaced the spiral cable in the steering wheel.

Edited September 16, 2021 by Jex
Grammar error

[Jex]

 🤔 problem sorted. Turns out the problem is a result of broken plastic tabs in the steering wheel horn button mechanism. There are 4 bolts that are insulated with plastic inserts that isolate both parts of the horn button that make contact when you push the pad. Under 2 of the bolts the plastic insulation was gone which meant both sides of the horn button were making permanent contact. This didn't come to light until the spiral cable was fixed. Toyota claim it was working properly when in left their work shop. If it was, it was a fluke. Anyway it was an easy fix. I made 2 plastic insulating washers to go under the bolts and now all working properly. Toyota sparky didn't diagnose it, I figured it out when I got back from the dealership.

Edited September 18, 2021 by Jex
Grammar error

[Tony Prodigy]

Nice work John. That solves the mystery of your +12v at the horn when not pressing the horn button. So the spiral cable is actually the clock spring unit right ?

[Jex]

Correct, Toyota call it a spiral cable but it's essentially the same thing.