Intermittent horn
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Actually the horn's very intermittent - just suddenly worked every now and again at random and unexpected times and now hasn't worked for a while. No pattern established so far.
The horn itself seems OK and works with a separate 12v supply.
It's an early (November 2002) TF with the Lucas fob. Lots of lurking and Googling is leading me to the Rotary Coupler or perhaps a relay on the BCU (apparently a common fault on later units) but any thoughts would be welcome and if it's one of those which would you suspect most and which is the simplest to fix?
If it's the coupler can it be something like a bad contact or do they just die and need replacing? I think I have been well warned about the airbag but any other hints would be much appreciated
What's that black canvas thing behind the seats for?
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However, what you need to do is to make a check to see if you have problem with rotary coupler or relay within MFU. You need to remove plastic surround of steering column, especialy upper part. You need to find white connector which plugs into rotary coupler. It is 6-way connector. Unplug it. There on positions 4 and 6 you will find Purple/Black trace and Black wires respectively. You need to bridge these two wires and you will see if horn works.
If horn works MFU relay is fine and you have problem with rotary coupler. If horn does not work, you need to replace MFU unit for new one as most probably relay is packed.
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- talkingcars
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FYI the coupler has 3 pairs of wires for other cars in the MG Rover range that had audio volume controls and cruise control.
Home to black Alfa Romeo 159 3.2 V6 Q4 ,green MGF VVC and red MG Maestro T16.
MG - the friendly marque.
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- Airportable
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The horn didn’t work on my car when I bought it, it turned out that a relay in the MFU had gone bugger up. There is however a couple of connectors between one & the other & there is a chance of intermittentsy.
M
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Check your electrical connections and earthing, apply 12volts directly to the horn and see if it actually still works before getting anymore complicated
"Keep calm, relax, focus on the problem & PULL THE BLOODY TRIGGER"
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- talkingcars
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<<<snip>>>Check your electrical connections and earthing, apply 12volts directly to the horn and see if it actually still works before getting anymore complicated
IIRC the horn has a constant live 12v supply with the earthing controlled by the MFU based on requests from either the horn buttons or the alarm.
Home to black Alfa Romeo 159 3.2 V6 Q4 ,green MGF VVC and red MG Maestro T16.
MG - the friendly marque.
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Play a grounding directly to the horn to see if it works, the point is to test the horn itself, personally I remove the horn and bench test it to be sure it works before anything else it’s easier to undo 1 bolt than buggerise about pulling steering columns apart to get at clock springs or cracking open control units to check relays.
"Keep calm, relax, focus on the problem & PULL THE BLOODY TRIGGER"
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- generous_dad
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The only irritation is that the horn contacts are tiny.
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- Notanumber
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Planning to try the 'two wires' test in the next few days, horn (singular) tests OK off the car.
I have found videos of the clockspring replacement but where is the relay hiding if that is the culprit?
Running out of time for the CT now, probably just put it in for a minor fail and get another 2 months to sort it!
(Did a similar thing many years ago with a Vitara we'd brought with us from England - UK Mot had expired, headlights wouldn't pass for LHD CT so just got a 'fail' which was legal enough for 8 weeks and an emergency trip back to the UK as the vehicle was in the process of registration! I don't make the rules...)
What's that black canvas thing behind the seats for?
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- Notanumber
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Link to the T bar's electrical diagrams https://www.the-t-bar.com/community/downloads/category/5-electrical-diagrams
2003 TF 135 sunstorm
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I now have a working French Horn again!
Didn't get a chance to do any more investigating so took it to the CT for a minor fail to get another couple of legal months to sort it.
Kept pressing the button all the way to the test centre just in case, but no joy - nothing at all, right up until parked outside.
Heard a faint beep from somewhere deep inside the test hall but just assumed it was another car. Tester returns 30 minutes later, 'All OK, nice car' and prints out the report...
I didn't dare say anything just in case he'd forgotten to test the horn, but once safely out of earshot the horn is definately working - and has done all the way home!
Thanks everyone for their input, at least I've watched so many videos about the clockspring and the MFU that I could probably do it in my sleep now if I have to
I know that MGs have their idiosyncrasies but this is ridiculous!
What's that black canvas thing behind the seats for?
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