red said:

Hi Luke,

I recall adding to one or several threads about horns and talking 'bout relays this and that. If the relay is not clicking in this means the fault lies in the primary circuit to the horn push. Dig out my thread where I did a step by step guide (all connections between the battery and the relay). Post again if you get stuck. If you think the problem is the horn push itself you will have to encounter what's called a "clockspring". this is a coiled up ribbon cable that connects the wires from the fixed column to the moving wheel. Two wires in this are for the horn and two more are for the airbag. Read the precautions about disturbing airbag circuits (battery off and wait 15-20 mins) and precautions about not turning the clockspring while the steering wheel is off (it has to be able to coil up and unwind with wheel movement so is set at half way when steering is pointing forward).

red

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Ziggy122 said:

Just because the Relay Doesn't Click - doesn't mean its wiring
The Relay Could be Shot itself

You need to apply a 12v supply
Posi to 86
Negi 85

And then test the Circuit for Continuity on pins 30 and 87

Remember You only need a small current to activate the switch


Also Check the Fuse - Might No look popped - but a continuity test will prove that

If the Relay Checks out okay - then Check the Horn By putting it on a 12v Circuit - With Suitable wire (like to battery to test it)

If horn don't work then horn is broken

And If they all work - Relay - Fuse and Horn

then test for a 12v circuit on the Horn Wires - that tell you If the current is getting there or not

IF no current - means there is a break somewhere

Ziggy

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Ziggy122 said:

Okay with the ""borrowed"" relay - Put a multi-meter set to 12v and put the Posi probe on one and Negi on the other
dont matter which the Multi meter will say 12v or -12v really

But when you press horn it should jump from 0 to 12/-12v

That way you know its not wiring - just the relay

But if you getting nothing then i'd be testing to see if Pressing the Horn itself is Giving a 12v Reading on the Fuse box's Pin 86 and 85
If Not then i'd say its more Horn wiring in the airbag then the wiring to the Actual Horn

Ziggy

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lukespalding said:

with the borrow relay put the posi and neg on what? a relay prong or the socket in the fusebox? Dont get you on that. :/
Sorry yea on the actual Horns Plugs

On the second bit you mean take the relay out and put the posi and neg on 86-85 and then press the horn and see if i get a 12v reading?
If it turns out to be horn wiring in the airbag any idea how I can go about fixing that?

Cheers
Yea Stick the probs IF you can into pin 85+86 positions on the Fusebox - might be too small - so paperclips come handy - just DONT short them

Luke

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red said:

Ziggy,

Luke said the horn itself was fine (he tested across the battery). As for relay, I hadn't eliminated it - the primary circuit to which I referred has the relay at its end. Systematic tesing will prove where the fault lies.

Luke,

If you find my old post can you paste a link so that I can review and clarify it?

Meanwhile, without wishing to repeat whatever I wrote elsewhere, the primary circuit is this (according to Mr Haynes):

Battery (+) to relay 3 (R3) Pin 85 via engine fusebox connector A Pin 1. Red wire. Should be 12V at all times.

Relay R3 Pin 86 to horn push via engine fusebox connector B Pin 21, "steering column multi-function switch" and clock spring. Black/pink wire. Should be 12V and drop to 0V when horn pressed.

Other side of horn push to earth via clock spring and "steering column multi-function switch". Black wire. Earth point is E3, LH inner wing. Should be 0V at all times.

The steering column multi-function switch is the side/dip/beam stalk. The horn circuit appears to pass through this unit but not through any contacts; appears to be used just used as a junction point.

So: If you "earth" the wire between R3 Pin 86 and the horn push, the relay should energise.

If you get the relay to click and the horn still doesn't sound, the secondary circuit uses Fuse F10 (15A) and the relay contact (Pins 30 and 87) to put 12V on the horn.

To test voltage on a wire if you can't get your meter probe into a connector, you can use a needle or pin (raid your nan's needlework box if necessary).

red

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lukespalding said:

Some of that I get but some i dont, like:

So: If you "earth" the wire between R3 Pin 86 and the horn push, the relay should energise. what the heck does that mean? :S

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red said:

Your horn is OK and your relay is almost certainly OK (you've substituted it).

You need to access that wire between Relay Pin 86 and the horn push and measure the voltage from there to earth. Should be 12V and drop to 0V when horn pressed. If it doesn't drop, short it to earth using one of your meter leads. Horn will almost certainly sound.

Access the horn push (I recall having to take the steering wheel off). Diss the battery before accessing. By the time you have the wheel off enough time should have elapsed to allow safe disconnection of the airbag connector.

Clean up the contacts or whatever, reconnect and test before putting the wheel back on fully.

red.

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red said:

Sorry, let me explain. To energise the relay coil, it needs 0V on Pin 86 (it already has 12V on Pin 85). It gets the 0V when the horn push is pressed because Pin 86 connects to one side of the horn push and the other side of the horn push is earthed (0V).

If you "earth" that wire (by that I mean connect it to earth/chassis/0V) you are doing the same as the horn push does so the relay should energise. It doesn't matter where along the wire you earth it; it could be at the relay Pin 86, at the engine fusebox connector B21, at the clockspring, at the horn push or somewhere along the length of wire between these parts.

You can either measure the voltage on the wire and press the horn (voltage should be 12V and then 0V) or you can earth it as described above to seewhether the relay energises. Personally I would measure the voltage.

red

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red said:

Luke,

If you want a quick test of the secondary circuit, pull the relay out and put a paperclip between the sockets for Pins 30 and 87. Make sure you get the right pin numbers though! The horn should sound because you are simulating a relay that has energised.

red

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lukespalding said:

Ok right so hypothetical here: I've got the steering wheel of and the horn push thing is infront of me now.

You need to access that wire between Relay Pin 86
I'm assuming you mean the wire that connects to that pin and then goes up into the cab to the horn push.

measure the voltage from there to earth, how would I do that?
you mean put one prong of multimeter(prosi?) on the relay pin 86 wire and put the neg prong on a earth point? or?

If it doesn't drop, short it to earth using one of your meter leads, whaat you mean? use the a lead to connect the horn push/relay wire to a earth point? which wud make the horn sound cause its earthed?

Sorry for being unbelievably stupid but I'm rubbish with instructions etc takess ages to get my head round them... :/

Cheers

Luke

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lukespalding said:

so the horn push button is the switch that activates it but the horn push doesnt have a live feed going thru its a broken earth circuit and when its pressed the earth circuit is complete which makes the whole circuit complete which then lets the horn sound? I'm prob wrong

if the above its anywhere close to right then I think I get what your saying.. :O

Cheers

Luke

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red said:

Luke,

Don't apologise here! This is good for me to try to ensure I write techy stuff at a level for others to understand.

You have correctly understood that I am referring to the wire from the relay up to the horn push and YES, to measure the voltage, meter (+) to the point under test and meter (-) to any good earth point. With a digital voltmeter it doesn't really matter if you swap the (+) and (-);it will just read a minus voltage. Also remember to select DC Volts on the meter. If it has autoranging you're fine; if not, select the 20 Volts DC range.

When I say "drop", I mean the voltage should go from 12V to 0V while you push the horn. It should go back to 12V when you release the horn.

My suggestion for "earthing" the wire is to prove that the relay would energise if it got 0V on that wire and YES, you correctly understood that I suggested using one of your meter leads to do the shorting (unless you happen to have a length of wire knocking around - if so use that).

Stick with this; you'll not only fix your horn but you'll increase your knowledge and experience of electrical fault finding!

red

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