Horns stopped working

[matgriff]

The horns have suddenly stopped working on my 2001 MY2000 MGF. The alarm functions correctly, so that part of the circuit & the horns/relay/fuses etc are all good, they just don't work from the horn buttons (both) I've double checked all the other fuses just in case the wiring diagram was wrong, but everything is OK.

I'm suspecting it must be the rotary coupler in the steering wheel ?

Are these problematic ? what's involved in replacing one ?


Thx

Mat

[50dwill]

Are you getting power to the horns? if you have not got a electrical tester just dab a temporary feed from the live on the battery to the horn terminal to check each horn.

[matgriff]

Hi

There's no power to the horns, that's why they're not working

The fault is between the buttons on the steering wheel & the relay,or the supply to the coupler... the relay isn't being energised by the buttons. although it is by the alarm.

[Mykel]

You probably don't need to replace the rotary coupler, there are six "wires" on the spiral inside, with the horns only using two of them. Check if two of the others are working and swap the pins both on the black button connector inside the steering wheel and on the white connector to the loom on the rear of the coupler.

[matgriff]

Hi Mykel, thx for the info. So basically on the MGF there are a couple of spare cores on the ribbon cable of the coupler ?? So it's possible to just re-locate the buttons to the spares (providing they have continuity) and then just move the connector loom pins to match ?

I've just looked at Rob Bell's guide how to get to the coupler and remove the steering wheel... that's a big help.

Cheers

[Mykel]

That's it, Mat. The coupler had been used in a wide range of cars, some of those with extra features like radio remote control or the shift controls for the steptronic gearbox, so there are some cores more than actually needed on a standard F or TF. On my first MGF, I used them for a retrofitted radio remote (taken off a Rover 45) actually.

[matgriff]

OK great I'll take a look at it as soon as the weather clears up a bit

[talkingcars]

Hi

There's no power to the horns, that's why they're not working

The fault is between the buttons on the steering wheel & the relay,or the supply to the coupler... the relay isn't being energised by the buttons. although it is by the alarm.

There should be power at the horns, they work when the switch connects the horn to earth.

[matgriff]

There should be power at the horns, they work when the switch connects the horn to earth.

Not according to the wiring diagram it doesn't ?

The 15A fuse F1 supplies the horn relay (normally open contact) which is switched to the horns. One side of both horns is connected to ground.

The horn relay coil is operated either by the Alarm circuit or the horn buttons.

I know for sure that the Alarm is sounding the horns, which means the Fuse/Relay & Horns are all good

Thx

Mat

[talkingcars]

You are correct about the power to the horns but according to my diagram it is fuse 7 in the under bonnet fusebox.

I think I'd start with popping the airbag off (2 x T30 screws) and earthing the different parts of the wiring there in.

[Geoff.F]

.

I think I'd start with popping the airbag off (2 x T30 screws) and earthing the different parts of the wiring there in.

I would consider disconnecting the horns and fitting a lightbulb..Neighbour friendly and less current,
Many of use know but must not assume all do. SAFETY NOTE. Before removing airbag, DISCONNECT BATTERY and leave for 20 minutes.
Geoff F.

[talkingcars]

Sorry, I forgot that one, MGR advised disconnecting the battery for 10 minutes before disconnecting the airbag.

[matgriff]

I pulled the wheel apart and checked the horn buttons, they are both OK so the problem is for sure in the rotary coupling.

Is the same unit used in all MGR cars or is it unique to the MGF/TF ?

I'm going to have a go at repairing the original, but I've seen loads of used good ones on ebay which all look similar for £10 so I thought I'd get a spare in case I can't get the original fixed... save me taking it apart twice.


Thanks

Mat

[Mykel]

The original part number is either YRC100170 or YRC100300, which are interchangeable. Apart from the MGF or TF, these were fitted to Rover 200/25 and 400/45 up to W-reg cars.

When you buy a used one make sure it was removed with the wheels in straight position an then taped to avoid movement of the coil.

[matgriff]

OK thanks will do.

I'll probably go to my local scrappy and get one myself to be sure it's taken off correctly

Mat

[matgriff]

Replaced the rotary coupler today and horns are all working again

I ordered a brand new one, £14.95 inc shipping, for that price I figured it wasn't worth trying to fix/bodge the original one.

Also stripped the rear calipers down & freed off the handbrake linkages cleaned out the old crud and sprayed a load of liquid grease down them.

Replaced the 15yr old gunky orange clutch fluid with all new DOT4, sucked it out of the slave cylinder with my mega sucker syringe.

Found out the my exhaust leak is the flex coupling (again)

All in all quite a productive day on the MG just gotta order a new front pipe...

[talkingcars]

15 year old brake fluid - lucky it hadn't frozen the system.
This happened on my daughters Rover 100 when she was away on a gap 6 months, in the end I got the garage to change the fluid, and they had to do it twice!