peanut
Active member
The sun came out today so I thought I'd have a go at fixing the horn on my S2 which hasn't worked since I bought the car two weeks ago. Funny how you resist the temptation to test the horn when you buy a new car. I thought if the following is useful to just one other member it is worth posting.
I started with the fuse . Surprised to find the fuse blown I thought this was going to turn out to be an easy fix but no such luck. Although the new fuse didn't blow on testing the horn it still didn't work so it was clear I would have to look further.
Short explanation of the horn operation. (best to skip this bit unless you want to add to your pain and misery)
(The horn relay (marked 53) is a single pole one way relay consisting of a internal coil between terminals 30 and 87 and a switch between terminals 85 & 86.)
12v+ is fed from the ignition switch to terminal 30 on the horn relay which is constantly live. It then travels through a small coil in the relay between terminals 30 and 87 returning to the horn button (brown/white). When the horn button is pressed, the 12v+ in this circuit is shorted to earth, via the horn button, through the steering column which then energises the relay coil. The energy field created, switches the relay switch on between the other two terminals 85 & 86. The 12v+ sitting at terminal 85 is then fed via terminal 86 to the positive terminal on the horn which is constantly earthed via the chassis thus sounding the horn. Clear as mud eh!)
The next step was to check the relay by substituting the fog light relay . After cleaning the relay contacts I could clearly hear the relay activating when pressing the horn so next I checked the voltage on all four relay terminals by using a voltmeter
Placing the negative lead on a good earthing point somewhere on the engine or chassis I placed the positive prod into each of the four terminals of the relay socket in turn noting the voltage.
Two of the terminals 86 and 30 should have permanent 12v+ the other two terminals should be at -0v because they are both switched live when the horn is pressed.
Having verified that 12v+ is at both the fuse and the relay the next step is to check there is 12v+ at the positive horn terminal when the horn is pressed (with ignition on)
If there is 12v+ at the horn terminal (yellow /black) check between the earth terminal on the horn (brown wire) and any nearby earth point on the engine or chassis using the resistance or continuity circuit of your multimeter. Alternatively just connect a wire to the earth terminal of the horn and a nearby earthing point and test again. If the horn still doesn't work ,(as mine did not, its definitely a new horn needed.
It took me 10 minutes to find the horn which is buried beneath the passenger headlight. There are apparently two on the S2 although I could only barely see the edge of one horn. (green arrow) The blue arrow is the temporary horn I fitted from a mondeo and the red arrow is the earthing point which was severly corroded
I managed with great difficulty to remove the two electrical connectors and when the rubber insulating covers were removed the terminals were revealed covered in rust and very corroded. The horns are unfortunately placed directly beneath the passenger headlight so that every time the headlights are on and it rains you have water pouring over the horn and connectors.
I started with the fuse . Surprised to find the fuse blown I thought this was going to turn out to be an easy fix but no such luck. Although the new fuse didn't blow on testing the horn it still didn't work so it was clear I would have to look further.
Short explanation of the horn operation. (best to skip this bit unless you want to add to your pain and misery)
(The horn relay (marked 53) is a single pole one way relay consisting of a internal coil between terminals 30 and 87 and a switch between terminals 85 & 86.)
12v+ is fed from the ignition switch to terminal 30 on the horn relay which is constantly live. It then travels through a small coil in the relay between terminals 30 and 87 returning to the horn button (brown/white). When the horn button is pressed, the 12v+ in this circuit is shorted to earth, via the horn button, through the steering column which then energises the relay coil. The energy field created, switches the relay switch on between the other two terminals 85 & 86. The 12v+ sitting at terminal 85 is then fed via terminal 86 to the positive terminal on the horn which is constantly earthed via the chassis thus sounding the horn. Clear as mud eh!)
The next step was to check the relay by substituting the fog light relay . After cleaning the relay contacts I could clearly hear the relay activating when pressing the horn so next I checked the voltage on all four relay terminals by using a voltmeter
Placing the negative lead on a good earthing point somewhere on the engine or chassis I placed the positive prod into each of the four terminals of the relay socket in turn noting the voltage.
Two of the terminals 86 and 30 should have permanent 12v+ the other two terminals should be at -0v because they are both switched live when the horn is pressed.
Having verified that 12v+ is at both the fuse and the relay the next step is to check there is 12v+ at the positive horn terminal when the horn is pressed (with ignition on)
If there is 12v+ at the horn terminal (yellow /black) check between the earth terminal on the horn (brown wire) and any nearby earth point on the engine or chassis using the resistance or continuity circuit of your multimeter. Alternatively just connect a wire to the earth terminal of the horn and a nearby earthing point and test again. If the horn still doesn't work ,(as mine did not, its definitely a new horn needed.
It took me 10 minutes to find the horn which is buried beneath the passenger headlight. There are apparently two on the S2 although I could only barely see the edge of one horn. (green arrow) The blue arrow is the temporary horn I fitted from a mondeo and the red arrow is the earthing point which was severly corroded
I managed with great difficulty to remove the two electrical connectors and when the rubber insulating covers were removed the terminals were revealed covered in rust and very corroded. The horns are unfortunately placed directly beneath the passenger headlight so that every time the headlights are on and it rains you have water pouring over the horn and connectors.
