Technical 2010 Active horn not working

[MrGman]

I’ve got a 2010 active eco, as the title says the horn isn’t working at the moment, a few weeks back it decided to go off randomly when it was parked up, to stop it until I had time to look in to it I disconnected the horn.

I’ve had a look at it today and the relay isn’t getting a signal from the horn switch, can anyone tell me if the horn runs through the ecu on these cars?

I haven’t had the usual airbag light come on when the clock springs fail, and I’ve rotated the wheel from lock to lock while trying the horn so I’m a little unsure where to go next.

ECU? A split in the loom somewhere? Clock spring?

Any help would be much appreciated.

 

[Steve126]

My horn stopped working because the clock spring had failed and I didn't have the airbag light come on, so it could be the clock spring.

 

[MrGman]

I've taken the clock spring off the car and tested the circuit with the horn button connected and it's a solid circuit so this leaves me knowing the problem is between the clock spring and the relay now.

I just need to find out if it does go via the ECU or not to be able to go any further.

 

[chris3234]

More then likely it does if you have mes you should be able to look at the body computer see if it shows horn switch pressed as one of the values it monitors


That being said clock spring seem the most likely issue

 

[Goudrons]

Is there not a seperate fuse for the horn, in the engine compartment fuse box, F10.
Have you checked that?

 

[MrGman]

Is there not a seperate fuse for the horn, in the engine compartment fuse box, F10.
Have you checked that?

I have checked the fuse, all fine, the horn works if you short the relay terminals in the fuse box.

It's the signal wire to the relay which is a switched -ve, when tested with the multimeter it's showing around 5-7v ??

 

[chris3234]

I have checked the fuse, all fine, the horn works if you short the relay terminals in the fuse box.

It's the signal wire to the relay which is a switched -ve, when tested with the multimeter it's showing around 5-7v ??

So you get voltage when you press the switch but not enough to trigger the horn?


Perhaps worth cleaning up any earth point you can find especially under the dash and the main battery one

 

[MrGman]

So you get voltage when you press the switch but not enough to trigger the horn?


Perhaps worth cleaning up any earth point you can find especially under the dash and the main battery one

Pressing the switch doesn't change anything, there is permanent voltage there but as it's a -ve switch there shouldn't be any

 

[koalar]

its a very simple system

battery
fuse
horn
relay
switch

works even without the keys in the car, ECU or body computer powered up

there's two separate circuits at the relay, the power side, the control side

both share the same battery voltage through F10 and are wired together

relay T03 is where i would start. If I pull it out, does it have battery voltage on two of its pins. If not have you got voltage to and from F10

if you swap it over for another in the fuse box does it work

control side, with the battery disconnected, black/green (probably) cable at the T03 relay it open circuit to earth and short circuit to earth horn pressed

 

[MrGman]

An update, the fuse box relay terminals are all doing as they should, it was me rushing at lunchtime that was at fault

Also tried

its a very simple system

battery
fuse
horn
relay
switch

works even without the keys in the car, ECU or body computer powered up

there's two separate circuits at the relay, the power side, the control side

both share the same battery voltage through F10 and are wired together

relay T03 is where i would start. If I pull it out, does it have battery voltage on two of its pins. If not have you got voltage to and from F10

if you swap it over for another in the fuse box does it work

control side, with the battery disconnected, black/green (probably) cable at the T03 relay it open circuit to earth and short circuit to earth horn pressed

The fuse is fine, the relay is fine, the horn works if you bridge the relay terminals, the horn button works, the squib works so I guess that leaves a break in the wire between the squib and relay??

you're right, the signal wire is black and green.

 

[koalar]

An update, the fuse box relay terminals are all doing as they should, it was me rushing at lunchtime that was at fault

Also tried



The fuse is fine, the relay is fine, the horn works if you bridge the relay terminals, the horn button works, the squib works so I guess that leaves a break in the wire between the squib and relay??

you're right, the signal wire is black and green.

possible

but not necessarily

you know the power side is fine by bridging the relay. Relay to horn to ground

the initial problem of horn stuck on hints at the relay, the switch, the black and green wire had a short to earth or the red and black wire (steering wheel towards relay side) had a short to earth. On the other side of the horn switch wire blue and black wire would not cause the horn to stay on, so we can ignore this for now

the two wires one from the relay and the other from the horn switch meet at the body computer. But its just an internal jumper. there's no electronics involved

do you have two live pins at the relay ?

with the relay in place. If you touch the green and black wire with a test light (incandescent bulb) other end on chassis ground does the horn sound

nothing is sent from the steering wheel. It just completes the path to ground

 

[MrGman]

The relay does have two positives yes.

I’m hoping to look a bit further later on today and will test a couple of bits you’ve suggested.

I massively appreciate your help with this

 

[MrGman]

Checking continuity with the battery disconnected:
Relay pin 30 is positive
Pin 87 is earthed
Pin 86 is positive
Pin 85 has nothing with the horn pressed or released.

Battery connected
Connected the black/green wire at pin 85 with the relay installed sounds the horn.

A couple of other points I can note, all other electrics on the car appear to work.
The skuttle drains were blocked and the skuttle was full of water, this has got through to the car and under the dash is a bit damp in some areas.

 

[irc]

Not trying to derail @koalar 's diagnostics but saw similar problem caused by chafing wires under the scuttle. When they got wet the horn occasionally made a sad little noise. Cleared duckbills, repaired wire (which happened to be the one for for the horn), re-covered with loom tape and all was OK.
Might be a shortcut.
EDIT: I seem to remember it being a purple and white wire, but I am colourblind...

 

[MrGman]

at the beginning of all this I noticed the wiring around the skuttle area was suspect, I had a quick look earlier and stripped most of the suspect areas back, certainly didn’t find anything to raise concern.

 

[koalar]

Battery connected
Connected the black/green wire at pin 85 with the relay installed sounds the horn.

i take it thats the green and black at the relay connected to ground and the horn sounds

if so great

 

[MrGman]

i take it thats the green and black at the relay connected to ground and the horn sounds

if so great

Yes sorry I wasn’t very clear

 

[koalar]

thanks all you need to do is move the earth along the path until you find the problem

be carful i have an eco and have noticed the wiring is slightly different

the next would be the other end of the green and black, pin 2 connector C on the body computer hopefully the problem lies here

i like to use an incandescent test light as limits the current to about 800mA connected to chassis ground

pin 18 connector H would be a pain as its on the back i might skip over and try the other end of the red and black

 

[MrGman]

Thank you very much for the diagram, so helpful.

I had a brief look earlier as I did think that might be the way to go, though it looks very awkward to get to it all!

I might have to pick a test light up as it’s something I’m lacking. Electrics have always been my nemesis but it’s something I’m trying to push myself into so I shall invest.

 

[koalar]

Thank you very much for the diagram, so helpful.

I had a brief look earlier as I did think that might be the way to go, though it looks very awkward to get to it all!

I might have to pick a test light up as it’s something I’m lacking. Electrics have always been my nemesis but it’s something I’m trying to push myself into so I shall invest.

the new LED computer safe type will not work as they will not allow enough current to activate the relay