For no known reason this afternoon the horn on fatty started blowing. It was sitting, parked, in the yard. I've tried unlocking, locking, starting the engine, stopping, opening and closing doors, bonnet, tailgate, all to no avail. Everything else works as it should but the horn won't stop blowing. As a quick interim fix I've disconnected the battery to shut it up and I can probably pull a fuse or something tomorrow when it's lighter (and a bit warmer), but any idea what on earth could cause this?

I've tried a search and can't find anything. It isn't the alarm by the way, it's the main horn and it's on constantly. Any help appreciated. Drives:
2010 FFRR TdV8 Vogue - Stornoway Grey
2010 FFRR TdV8 Vogue SE - Zermatt Silver
1998 BMW E36 M3 GTII

I'd be checking the horn button on steering wheel, possibly jammed. Perhaps a sticking relay?

Thanks, I will be checking in the morning, too damned cold at the moment! Just seems odd that it started all by itself. Drives:
2010 FFRR TdV8 Vogue - Stornoway Grey
2010 FFRR TdV8 Vogue SE - Zermatt Silver
1998 BMW E36 M3 GTII

continuously or more like an alarm sound? 2011 L322 Autobography - a lot of bells and some of the whistles...owner with no idea!

No, it's continuous, so it isn't the alarm.

I'm going to try the horn relay as a first fix, it could well have failed to earth which would explain things. In the meantime I'll have to run with the relay removed until I can get one to test. Drives:
2010 FFRR TdV8 Vogue - Stornoway Grey
2010 FFRR TdV8 Vogue SE - Zermatt Silver
1998 BMW E36 M3 GTII

Well, I didn't have to run with the relay removed, one of the twin tone horns has packed up and now doesn't blow constantly. I have changed the relay, but obviously it's all still the same.

I'm wondering if one of the horns has failed to earth for some reason, is this possible? Mind you, for that to be the case, then I assume there would have to be a constant 12v supply and the switching is on the earth side. Drives:
2010 FFRR TdV8 Vogue - Stornoway Grey
2010 FFRR TdV8 Vogue SE - Zermatt Silver
1998 BMW E36 M3 GTII