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mgf
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Discussion Starter · #1 ·
Has anyone found that the horn refuses to work from the standard steering wheel push button. I took off one of the two horns and it worked when wired up to the battery. Is there a relay on the fuseboard that gives trouble. I'm not great on electrics other than positive and negative feeds make a thing work. Would the steering wheel have to come off to examine the push switch. Any help would be appreciated as to get an autoelec here is next to impossible with long waiting times.
 

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Since under your name says MGF I will assume you have MGF. In that case horn relay is paet of MFU (Multi Function Unit), which is bolted onto back side of your fusebox, and cannot be replaced otherwise then to replace whole MFU.
In order to inspect horn buttons, you wouod need to remove airbag. However, if you remove upper part of steering wheel cowling, you will expose wires that come from horn buttons. By inspecting them you will check if you have problems with rotary coupler.
 

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2002 MG TF VE51FTF
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I suspect it is probably the rotary coupler which are readily available and not too expensive here (拢20-拢30) but Ireland?
The link below explains how to maybe repair one!!! personally I would get another one, the last bit says it all "if you have done it wrong the airbag may go off"
It's not a difficult job to change and as long as you observe the safety rules you will be ok, just read up on it as you should have the wheels straight ahead and the coupler should be mid travel when it's fitted. If it turns out to be the MFU (no idea how to do this) look on the bright side you now have a spare coupler.
Inside the Rotary Coupler (apttony.co.uk)
 

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mgf
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Discussion Starter · #4 ·
Since under your name says MGF I will assume you have MGF. In that case horn relay is paet of MFU (Multi Function Unit), which is bolted onto back side of your fusebox, and cannot be replaced otherwise then to replace whole MFU.
In order to inspect horn buttons, you wouod need to remove airbag. However, if you remove upper part of steering wheel cowling, you will expose wires that come from horn buttons. By inspecting them you will check if you have problems with rotary coupler.
Thanks for the reply deepfat and Riverside. The horn was recently only working now and again. I thought it was the horn units and took them off. I then fiddled around with getting a good earth etc and they worked again. The last few days while driving I have been pushing the buttons and got the odd spurt but they seem to be gone all the time now. Is it a common issue with the MGF?.
Maybe putting on a push button on the dash would work........ Will that pass the MOT???
 

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I do not think push button on the dash would pass MoT. You need to have it on your wheel.
Unless the legislation has changed in past two years a horn can be just a push button anywhere in a position where the driver can easily access. My brother has a TF which when he bought it had a separate horn button under the dash, it appeared to have been fitted due to the pektron relay issue as it had been wired with around three separate relays. My brother took the pektron unit off, refitted new relays and then re wired the horns back to the pektron unit.
 

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mgf
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Discussion Starter · #7 ·
Unless the legislation has changed in past two years a horn can be just a push button anywhere in a position where the driver can easily access. My brother has a TF which when he bought it had a separate horn button under the dash, it appeared to have been fitted due to the pektron relay issue as it had been wired with around three separate relays. My brother took the pektron unit off, refitted new relays and then re wired the horns back to the pektron unit.
What if I got a complete new steering wheel with push buttons for the horn would that work or is the horn connection on the steering shaft or column??
 

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If you suspect the horn buttons take the wheel off and check them for continuity but it is unlikely they both failed together, remember if doing this you still have to disconnect the batt and wait 15m. If you can find a wiring diagram (I think 1 of the forums have them T Bar?) you can check out the feed as well, I'm unsure of the wiring so can't advise.
 

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What if I got a complete new steering wheel with push buttons for the horn would that work or is the horn connection on the steering shaft or column??
Horn buttons have earth connection within the steering wheer. Then horn buttons connect to rotary coupler below steering wheel. Then rotary coupler connects to wires along steering column. These wires from steering column goes to MFU unit behined fusebox. Then from MFU unit wires go to horns.

You need to find where is the problem. Otherwise replacing parts might not solve your problem.
 

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Unless the legislation has changed in past two years a horn can be just a push button anywhere in a position where the driver can easily access. My brother has a TF which when he bought it had a separate horn button under the dash, it appeared to have been fitted due to the pektron relay issue as it had been wired with around three separate relays. My brother took the pektron unit off, refitted new relays and then re wired the horns back to the pektron unit.
Fair enough. If it is different then in EU, then I have nothing to add.
 

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mgf
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Discussion Starter · #11 ·
Fair enough. If it is different then in EU, then I have nothing to add.
Well just locked the car and opened the bonnet and the alarm horns went off so we know now the horns are fine. Tried pushing the steering wheel buttons and nothing happens. What can you conclude from that ?
 

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Well just locked the car and opened the bonnet and the alarm horns went off so we know now the horns are fine. Tried pushing the steering wheel buttons and nothing happens. What can you conclude from that ?
From that you can conclude that horns are working correctly and relay in the MFU unit is working correctly. So the problem is either in earth connection of horn buttons in the steering wheel, horn switches itself or rotary coupler.
 

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Horn buttons have earth connection within the steering wheer.
The horn buttons on a TF earth through the rotary coupler - I assume the MGF is the same.

(I discovered this whilst fitting a TF steering wheel to a ZR some years ago - the horn buttons on the 25/ZR and 45/ZS earth direct onto the body of the steering wheel, so it needed a little swapping of components to get the ZR horn working with the TF steering wheel).

I too would think a worn rotary coupler is a fairly likely candidate to be causing the fault.
 

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mgf
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Discussion Starter · #14 ·
From that you can conclude that horns are working correctly and relay in the MFU unit is working correctly. So the problem is either in earth connection of horn buttons in the steering wheel, horn switches itself or rotary coupler.
Thanks Roverlike it looks like the steering wheel job so is to be done. That means a garage as I wouldn't risk the airbag going off. Has the airbag got a best before date for the MOT.??
 

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The horn buttons on a TF earth through the rotary coupler - I assume the MGF is the same.

(I discovered this whilst fitting a TF steering wheel to a ZR some years ago - the horn buttons on the 25/ZR and 45/ZS earth direct onto the body of the steering wheel, so it needed a little swapping of components to get the ZR horn working with the TF steering wheel).

I too would think a worn rotary coupler is a fairly likely candidate to be causing the fault.
Yes, you are correct. I forgot that difference in case of MG F/TF cars. Horn buttons are earthed through rotary coupler.

However I noticed this quote from OP:

The horn was recently only working now and again. I thought it was the horn units and took them off. I then fiddled around with getting a good earth etc and they worked again.
So I wonder if OP do have horn buttons earthed on the steering wheel?
 

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Thanks Roverlike it looks like the steering wheel job so is to be done. That means a garage as I wouldn't risk the airbag going off. Has the airbag got a best before date for the MOT.??
From manuals it is said that airbags need to be replaced after 10 or 15 years. However, EU MoT rules does not look into this and you do not need to change anything. I do not know if there are differences in MoT where you are checking your car.
 

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I understand the 10 to 15-year date for airbags is primarily for very humid countries where even synthetic fabric can degrade when in storage. Having last year, crash tested 13-year-old airbags and they worked as expected.
 

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When my horn didn't work for the MOT my friendly local auto electrician located a push button in the dash.
It then passed MOT
 
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