I had a recent problem with my Fiat Marea 1.8 ELX (1998). First the airbag warning light came on then the horn stopped working and the latest problem was that the radio controls on the steering wheel did not function. I wasn't sure if these were connected but as all of the problems seemed to be centered round the steering wheel i decided to take a peek. I got to the steering wheel securing nut and didn't have a large enough spanner to fit so decided not to go any further but unplugged the multi plugs i could see and refit them hopping this would cure my problems, but the problems remained. I then called an auto electrician who pointed out that all the wires run through the stalk unit just below the steering wheel and that this unit was at fault and would need to be replaced which would be fairly expensive (The modified part was £202 inc vat at the time of writing this). I decided to bite the bullet go ahead and replace this unit. The unit comes complete with the stalks flasher unit and all the connections for the multi plugs. Replacing this did in fact cure all the problems. The reason I am posting this is because i could not find an answer when i searched the forum and thought this info would be of interest to someone out there. Hope it helps. I include a diagram of the unit I have replaced...
View attachment stalke unit.pdf
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So far only the horn failed on my car. I ran to wires to a micro switch mounted on the bottom of the steering column shroud to avoid replacing the whole unit, thanks a lot for posting though you mention modifoed unit, does that mean they fixed the probs as this is an assembly that often fails.

Yes this was a brand new unit and that fiat had modified in some way, I’m not sure what difference there was from the original one but that’s what the guy told me. All problems I had were fixed. The auto electrician I was talking to said that it’s possible that my headlights could have also stopped working. I guess it could have effected all electric’s that is controlled from the steering wheel stalks?