Horn failure after COM 2000 repair

[DaveyRapier]

I don’t know what I was getting before unfortunately, I was just pleased it was working.
Although my friend is breaking a 2001 hdi (D9 I believe but not sure, has crystal headlights etc) I was going to get the com out of it but unfortunately it has the older type controls with thin stalks, also the wiring is different there’s a plug in the centre of the airbag at the back but I put my meter on his horn and it has 12v at the wheel, maybe the older system is different?
I cleaned all 4 contact points on my wheel when changing the com, even if I pull the wire off the airbag and short it directly to earth the horn doesn’t sound..... is there anyway of bypassing this relay to check it hasn’t failed?
Bloody French electrics

[steve_earwig]

We call the earlier D9's "semi-mux", they are mux but don't have as much of the stuff as the later "full-mux" cars. One of the most obvious changes is the com2000, on the earlier cars it's just normal (not any more it aint ) 12 volt switches.

It was just a thought, unlikely I know. If that is indeed the fuse you should be able to sound the horns by giving it 12 volts.

Most of it is German...

[DaveyRapier]

Ok finally cracked this, the only problem was my stupidity took the airbag off again and pulled the spade connection off the back and touched it to the earth cable (T15 torx screw) and it sounded. Amazingly when I tried before I was touching it to the centre (metal) of the steering wheel which was quite grubby.
The problem was I had cleaned the 4 contact points but had not cleaned the point where this earth connects which was not allowing the signal to complete the circuit.
Gave this point a quick rub with emery paper and rebuilt. All is now working
Steve earwig many thanks for sticking with this thread throughout my efforts, cheers

[steve_earwig]

Yay!! \o/ Not a problem, I just didn't want to leave you in the lurch.

The steering column could even be isolated from earth, with nylon bushings and plastic joints. Anyway, just glad you got it sorted.

[Doggy]

Well done gentlemen.
Good to see problems like this getting resolved, no doubt help someone else / encourage others.

[GingerMagic]

So does this mean this was the issue all along?
If so at least you now have a spare Comms unit