Horn not working

[james12345]

Okay, so the Chim failed the MOT on the horn not working, and I've been tearing my hair out ever since as to why.

Fuse known to be good - swapped with others, other circuits still working - horn not.
Relay known to be good - swapped with others, other circuits still working - horn not. No clicking at relay when horn button pressed.
Not getting 12v at horn terminals.
I'm not getting 12v at the horn switch either (either within the button or the purple / black with within the cowling). Not surprising if I'm not getting 12v at the horn itself though.

Here's the clincher - it's just back from having new outriggers. Could there be something there that's been disconnected / changed / missed that may be stopping the horn from working?

I'm now beyond stumped!!!

[jamienshelly]

Try holding the horn button down and turning the steering wheel round, if it works in 1 or 2 places then your slip ring is worn or dirty.

[s p a c e m a n]

You won't get 12v at the horn button, it's an earth, the button you press works by completing the circuit to earth. As above, may be the ring or button etc, try earthing the wire from before the steering wheel.



The wiring diag (as if that can always be believed) shows a purple black wire from the button to a connector block where it swaps over to purple white all the way to the horns.

If you're not getting 12v at the horns then that will be where your problem lies, the get their supply from the heaters and there's nothing else on that spur so if that wire has failed the horns will be the only things that don't work.

I would run a bit of wire from the radiator fan live, or battery if you've got a long enough bit of wire and then press the horn button. If that works you just need to tap into a live somewhere to fix it. Is it an MOT requirement that the horns work with the ignition off? I would tap into the fan circuit.

Edited by s p a c e m a n on Monday 21st April 11:08

[james12345]

Tried earthing the purple/black behind the cowl - still no horn. Any idea where the connector is in this wire? Might be the next best place to check...

[s p a c e m a n]

It's going to be the live if you have none at the horns, I would try that first before taking the dash off.. Just nick one from somewhere (make sure the ignitions on depending on where you steal it from) and give it a go.

[james12345]

Well the dash is half off anyway, so can easily check under there! Just replaced the alarm as the old one was faulty - perhaps I could have dislodged something?

If I were to steal a live from somewhere, what would be the best place to connect it to? All the way to the horns themselves, or something around the fuse box to have the relay involved?

[s p a c e m a n]

No idea where the block is, the schematic calls it block h. It's the only one I can see with a loop of white wire going between two pins that are next to each other, which are the pins for the horn purple/black and purple/white on the other side of the loop.

I would run a wire from the radiator fan live at the fans, it's in the general area and there's a plug connection there. It doesn't really matter where you're linking it from at the mo, just find a live for fault finding and then if that's your problem figure out the closest solution.

Looking at what else is connected, that block might be under the steering cowling, its all flasher switch/ indicator etc.

Edited by s p a c e m a n on Monday 21st April 11:39

[james12345]

So no luck -the live by the rad is only going to be live when the fans kick in, there's no permanent love there to test from.

Reading back through your earlier post, you say the only other thing in that spur is the heater - do you mean the heater fan, as that isn't working either at the moment. I put it down to a bad heater control box, but having got that it, there's no burnt connectors on it.

Could well all be linked -with the dash to off there nothing that's obviously this connector though!

[s p a c e m a n]

Yeah, the diag said that it gets its feed from the blower.. think the lights or indicators were further on too..

[s p a c e m a n]

Power from the heater speed switch from the look of it.. Hows that work then..

Edited by s p a c e m a n on Tuesday 22 April 19:42

[ukdj]

s p a c e m a n said:

Power from the heater speed switch from the look of it.. Hows that work then..

Err look at the diagram a bit more closely, you'll see that the horns are connected to the -ve ground side of the heater motor not the +ve, the live appears to come from the wire labeled PW (purple/white) which is connected to BLOCK K wherever that is in reality?

The bible says purple/yellow is horn to horn relay and purple/black is horn/horn relay to horn push switch.

Hope that helps ...

Regards

UKDJ

[s p a c e m a n]

That's where I get confused on it all, because the horn button is an earth

[ukdj]

I believe the horn button completes the earth circuit to the relay which then switches the live to the horn(s)

Regards

UKDJ

[james12345]

Yep, block K appears to be where it's all at -and in keeping, this also has a connector to the heater on it from what I can see... Buggered if i can find it though!

[james12345]

Also, I'm still holding out hope that someone who's had their outriggers done will pop along and say "Don't forget to reconnect the plug that's in position xx, or your horn won't work! "

[james12345]

Right - fixed it!

I'd previously swapped the relay with the one at position 1, both marked as MO404. Decided to try to swap with another - also marked as MO404, the handbook shows it as man beam - but this one was brown rather than yellow.

Pressed the horn, and it only bloody worked!