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MG MGF Technical - Horn failure

My horns have stopped working when pressing the buttons on the steering wheel.

The fuse, relay and horns themselves still function, since these can be tripped by the alarm function, so that side of the circuit is okay.

Niether button will sound the horns, so the problem must lie somewhere in the steering wheel rotary coupler or earth connections between the buttons and the chassis ground point.

I have the circuit diagrams etc, but am unclear about where the various connectors are. As far as I can see they seem to sited on the driver-well fusebox, and possibly behind it.

My questions are....

1. On the fusebox plate, there are 2 bolts at the top. Does the fuse box drop down/away if these are undone.

2. Is it easy to remove the horn buttons from the steering wheel without damaging either the button or the wheel?

I need to check for continuity but am reluctant to start pulling things apart until I've got a better idea of what is what.

Tony Thompson

1. yes
2. no, better said, never tried
I have a spare steering wheel in the cellar. Can look up if required.

I think it's not required in your case to advise on disconnecting the battery at first, cause you know.

Whatever you decide. Take care on the rotary coupler turning anywhere. After pulling the steering wheel off I immidiatly suggest to secure against rotating by applicating of a piece self adhesive tape to the coverplate and side.

Good luck
Dieter K.

Thanks Dieter.

I'm not sure of the design of the rotary coupler or whether it's at fault - tried a test of steering full lock left: press horn: central: press horn: full lock right: press horn. The horn did not work in any position.

Do you know if it's a single or multiple point contact for the circuit on the coupler? If it's multi-point then I feel that the break in the circuit is unlikely to the coupler itself.

The service manual diagram for removing the steering wheel shows the horn buttons lifted out of the steering wheel face(towards the driver) and simply says "Release 2 horn switches from.....", without explaining how (typical!!!), and without explaining if they can be gently levered out or if they are retained by clips. Any ideas?

If I can get one out easily, then I can test for both live and earth continuity at that point, which would greatly simplify matters.


I had the same problem on mine - horns just failed to work one day. As it is under warranty I took it straight to my dealer who found it to be the rotary coupler.
An important point to note is the drivers airbag is also de-activated, so I suggest you get it sorted pdq.
(it took the dealer about 30 mins to fix)

Cheers, Bob
Robert Tulloch


A very good point - thanks for pointing it out.

Have to admit though, I'm still not convinced it is the rotary coupler.


Neither am I.
Have you actually checked the fuses... I think the alarm itself feeds the horn, as it does the flashers, so if the fuse for the horn has gone then it will still operate via the alarm (and visa-versa)

Will Munns

>An important point to note is the drivers airbag is also de-activated,

?? slights doubts. Was the SRS warning light off ?

The rotary coupler is inside a flexi strip with I think about 5 different wires. The wires don't break, but the crimp connectors at both ends are ... err, crap. Not good design IMO.

Dieter K.

good point Will, another area of double fuse for alarm and the fused item.

The fuse F7 under the bonnet is okay. This feeds both the horns and, according to my info., the ECU alarms.

The flashers are driven through fuse F4 (also under bonnet).

I need to check the SRS warning light.


My Owners Handbook shows Engine Compartment Fuse 1 for stoplights and horn and Fuse 7 for Engine Management System (all page 91)

says under the bonnet is a fusebox, fuse 7

Ok for the horns the rotary coupler has one wire and a ground.
PB - Purple with black stripe, find this wire on the car side of the coupler, pull it to earth (black wire) and see if the horn sounds, if so then it is the coupler, if not thn it might be the fuse, the wireing (see the web page, it lists the connetcions between all parts or the spade connectors on the horns (has the garage removed them?)

Will Munns

Will I agree with the content on Diters site, I was just repeating the info shown in the MG Owners Handbook supplied with my car.

Is it worth Tony checking fuse 1?

Did the fuse allocation change across MYs ?

>Is it worth Tony checking fuse 1?
No harm in it

>Did the fuse allocation change across MYs ?
I don't know / not that I heard of, but it wouldn't surprise me
Will Munns

Christ it's cold out there but ... just pulled out Fuse 1 (under bonnet) and horn stopped working, put it back in and horn started working!

Suggest holding the fuse box lid the right way round and then checking fuse 1.

On my car, standing at the front facing towards the rear, fuse 1 is on the furthest right of the row of fuses (as shown in Owners Handbook).

If you pull the fuse box lid off and simply turn it over horizontally then the horn appears to be protected by the fuse on the left side of the row.

I suspect that to read it properly you need to sit in the fuse box and get somebody else to refit the lid, then all appears OK.



Just got home.

SRS is NOT indicating a problem.

The confussion of the fuse number:

The handbook does refer to Fuse No 1 as the horns & stop lights.

Rover's electical diagrams refer it as F7 for Alarm ECU & horns!


Need to check this out further but short but short of time now.

Will get back later.


>Did the fuse allocation change across MYs ?

Nope, they didn't (IMO).
I only know of wrong printed stickers on the fuse box lid (early cars) and of wrong diagram regarding the central locking system. Owners Manual isn't also a writing in which I put many trust :)
See bulbs section at early manuals an have a laughter.

Mind you on the new'ish fuse webside
Very last from mgtf documents. The should have learned writing in 7 years.

If we aggree on wrong diadram sb19.jpg, then I correct that drawing. I assume the other 6 of seven will be wrong written in the diagrams as well ? *mirrored*
Only No. 4 HAZARD LIGHTS in the middle may be marked correct ?

Very interesting again ;)

Dieter K.

Me again,

no more confusion.
Looked up on newest docs. Yes they are the same as the old.
- MGTF Owners Manual 1...7 is different to the diagrams
- Electrical descriptions 1...7 see above
- Electric diagrams, are different to above documents.
- Screen print on bonnet fuse box cover is OK

I think it's easier to modify/re-work the diagrams cause normally nobody has them and I worry about wrong things on the webside ;)

1 is 7
2 is 6
3 is 5
4 is 4 'Hurrey !!
5 is 3
6 is 2
7 is 1

dead easy, if known ;)
Anyone out there who approves ?

Dieter K.

When I had my problem, which was put down to the rotary coupler, the SRS light dwas NOT illuminated, yet the dealer was quite clear, the airbag was deactivated.
Robert Tulloch

"I worry about wrong things on the webside ;)"

Dieter - your website is the highlight of this bbs and a model for all other 'information sites'. I am sure that there are very few wrong things and even more sure that the few are caused by other people, not you :-)

@ Robert, strange, of course :(
I wonder which wire.

Anyway, I modified sb19.jpg, but not the other.

i.e looked up Fuse 3 on sb10.jpg.
Dooh ! they swapped by coincedence.
Looks like No 6 in truth ?
I think the correction works are for a different new thread later.

Just forget the above suppose on mirrored fuse numbers. It's not dead easy, but more difficult.

Dieter K.


In answer to your questions:-

1. <<On the fusebox plate, there are 2 bolts at the top. Does the fuse box drop down/away if these are undone.>>
Yes, I believe it does. The horn relay is contained in the Multifunction Unit which you will be able to access.

2. <<Is it easy to remove the horn buttons from the steering wheel without damaging either the button or the wheel?>>
Don't know because I have never done it. But I would suggest that in all probability your problem lies with the rotary coupler as it is unlikely that both buttons would fail at the same moment and they are wired in parallel. Find the purple/black wire coming from the coupler and check that it is being earthed when you press a horn button. If not then as a final check make sure the black wire at the coupler is earthed all the time. If the black wire is OK and the purple black is not being earthed by the horn buttons then the problem definitely lies in the coupler. Or of course you could be lucky and find the the socket on the coupler has come loose!

Ensure you disconnect the battery for at least ten minutes before attacking the rotary coupler as per the Airbag Warning and make sure the steering wheel is in the straight ahead position.

Good luck

Bruce Caldwell


Diagram shows fuse 1 as the most RIGHT fuse when facing the car from the front
Fuse No Amps Function
1 15 Stop lights & horn
2 15 Cooling fan
3 15 Air conditioning fan
4 10 Hazard Warning lights
5 15 Central door locking & alarm
6 30 EMS
7 30 EMS

CD - Electrical Circuits

Diagram shows fuse 1 as the most LEFT fuse when facing the car from the front
Fuse No Amps Function
7 15 Alarm ECU & horn
6 15 Radiator fan
5 15 Air conditioning fan and compressor
4 10 Hazard Warning lights / instrument pack
3 15 Alarm ECU
2 30 EMS relay module / alarm ECU
1 30 EMS relay module

Got in too late last night to do anything!

Its very cold here, but I hope at lunch time to check and see if removing the fuse stops the horn sounding when tripping the volumetric alarm.

Looking at the service manual diagram, it looks as though ff you remove the steering column nacelle, it may be possible to see the spade connections on the rotary coupler. Anyone know for sure?


Thanks Bruce

Just checked that removing the 15A fuse at the right most position when facing the car stops the volumetric sensor from sounding the alarm/horn so....

CD - Electrical Circuit

Fuse No Amps Function
7 15 Alarm ECU & horn obviously the right one.

Far too cold out there to start disconnecting the battery, waiting 10mins, removing steeering column nacelle, while fingers go white, then black, and then drop off!


Just tested it all.

Definitely the rotary coupler. Earth from coupler to chassis okay. Purple/black feed between coupler & ECU okay. Short both at coupler connector and reconnect battery....horn works!

Anyone changed the rotary coupler? Easy to do?



Just had a look at your site re: steering wheel & rotary coupler. Looks fairly straight forward to get at and to remove the coupler.

It may well be simply a broken / loose connector, but if there is no sign of such, then it might be prudent to fit a new one.

Any ideas on cost?



>broken / loose connector

You can measure this easy in advance when you hold the part *secured with tape* in your hands.

The 'plastic can' is easy to open.
There are some funny looking parts on the outer upper diameter, looking like a switch. Acted from the turning cover plate.

This thingy is of no importance, but just confusing.
I was very careful and didn't know at first what they are good for..... They are for nothing (at the MGF). One of them is a transport secure gap. I think a 'break off pin' was in there before they install at the factory. Secures from unwanted turns. You may use that location to apply the sticker tape.

Though make sure NOT to turn the cover plate none controlled.
I recommend to find a strategy how to get this done.
I.e. turn a known count of rounds to the release direction and write that count down.
Then get off the cover and repair, but don't turn cover versus body, unless counting this and writing/adding to the above.

The number of wind counts (spelling ?) must be the same when you put it back.

The strip connector is a standard but OEM design part.
like but worst quality (IMO)

Single spade connectors are simply crimped to the ends and the spades themself are pushed into the case (secured as usual at other connector cases). I didn't pull out, but recall seeing the crimp ends.
Really bad. That is IMO no longer allowed to be designed in this way for new cars. Better technical solutions are common today.

Hope this makes sense and you get what I talk about.

Good luck
PS take pictures for your site ;)
Dieter K.

Thanks Dieter,

It looks extremely delicate and since it play a significant role in the SRS airbag operation, and that I have no way of testing it, I'm inclined to be a coward & get my Rover dealer to replace it and then diagnostically test it after.

The time to replace the coupler must only be about 1 hour in total, so it should not be too expensive and I will have a lot more confidence in it after they test it.

After I posted my last mail on the thread, I decided to remove the airbag and steering wheel. That allowed me to test the horn buttons directly and also confirm that the connector above the coupler was not broken. Both were okay.

I took a couple of pictures at the same time.

It's also worth mentioning that in removing the steering wheel nacelles, one of the clips on the lower half broke, so that the two halves no longer clip together fully. Bloody plastic parts!! So that will have to be replaced as well. Maybe I was too forcefull in trying to split them, (the clip could have age hardened as well), but with no way of knowing how they are clipped together, it may be inevitable that something of this nature gets broken!


Yep, sufficiant decision IMO. I think it's best in this way.

I wrote so many to make you sensitive enough on the really delicate works. This is not just DIY like mounting a cigar lighter.
Dieter K.

Hello mate,I dont think your cars got a problem its your hearing!I know you,you live down the road.We had a neighbour hood watch meeting the other day about you,and we were complaining that we constantly hear you beep that beeping horn!Get it sorted lad, enough is enough!Go get your hearing sorted out,trust me its alot cheaper!I know off hearing aids which can be used with the hood down,so let me know if you need their address!Well hope you understand what the problem is now,cos if you havent Ill have to send the boys round to make it clearer!Cheers prt enjoy your Sunday. Jassy


Hmmm!!! Can't be me! The horns' NOT working !!

Or maybe, if you think it is me, how about some sort of idea of where you live? :-))


<<We had a neighbour hood watch meeting >>

So the hardtops are safe then!!
Bruce Caldwell

Well spotted Bruce.

E-mail on it's way.


This thread was discussed between 05/01/2003 and 14/01/2003

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