2000 540i/6 horn activating by itself

[bssmi]

Hi guys,

I used the search, but nothing came up with the same issue. I have a 2000 540i/6 with the M steering wheel and it has recently started to have issues with the horn suddenly activating by itself while driving. I pulled the fuse for the horn so that has temporarily solved the issue, but the fuse also apparently controls central locking so now I can't unlock the doors with my remote anymore. Therefore, I would really like to fix this issue so that I can put the fuse back in and get central locking working again.

Does anyone have any ideas on what might cause the horn to activate itself while driving and what might fix it?

Thanks in advance!

[BimmrMeUpSnotty]

How many miles on the car? Does it happen randomly? Steering wheel angle? Could be the clock spring ribbon cable frayed and the copper veins are shorting out. Just a guess.

[pleiades]

I second the idea that something's shorting out. Incidentally ... has the car cabin been exposed to any particularly hot temps in recent days?

[JimLev]

Or it could be the horn relay under the lower drivers side dash panel. It's just below the headlight switch.
I'd first suspect the clock spring like snotty said.
You could pull the relay and then put the fuse back in.....are you sure the horn and central locking are on the same fuse? (I didn't look at the wiring diagram)

[BimmrMeUpSnotty]

Oh yeah, relays always do go bad.

[bssmi]

How many miles on the car? Does it happen randomly? Steering wheel angle? Could be the clock spring ribbon cable frayed and the copper veins are shorting out. Just a guess.

The car has only 78k miles (it sat undriven for a long time by the original owner). It happened on one particular drive for the entire drive (about 15 miles). I had to keep tapping at the airbag to stop the horn from sounding off for most of the drive. Steering wheel angle was straight for the most part (highway).

Where is the clock spring ribbon cable and is it hard to access? Thanks a bunch for the help!

- - - Updated - - -

I second the idea that something's shorting out. Incidentally ... has the car cabin been exposed to any particularly hot temps in recent days?

There was no major change in temperature before this occurred. Thanks for chiming in.

- - - Updated - - -

Or it could be the horn relay under the lower drivers side dash panel. It's just below the headlight switch.
I'd first suspect the clock spring like snotty said.
You could pull the relay and then put the fuse back in.....are you sure the horn and central locking are on the same fuse? (I didn't look at the wiring diagram)

I'll have to take a look at the horn relay like you mentioned. I'm going to look for a diagram/diy of it.

I think that the horn and central locking use the same fuse because immediately after pulling the fuse, the horn turned off and my central locking stopped working. (The car stopped locking itself above 15mph and my remote control stopped working).

Thanks for the help!

[BimmrMeUpSnotty]

Check the relay first, with that done, if the horn is still going nuts, then move on the the clock spring.

To access the clock spring, you take the steering wheel off. Disconnect the battery before you do so, let the car sit for 16 minutes so it can go to sleep. 2 torx screws, 25's I think, throught the slits on the rear of the steering wheel spokes. These release the airbag. With the battery disconnected, you can unplug the airbag wire and steering wheel controls. Those plugs were plugged into the clock spring. You must take the steering wheel nut off and the wheel should come out. I would check the contacts where the airbag makes contact with the wheel, make sure the springs have the connection free, maybe that's all it was. Clock spring, really no way to check it, order a new one and install it. And for God's sakes, don't let your goofy friend play with the new spring, they come with a piece of tape keeping the clock spring in place. You peel it off when you are ready to replace the steering wheel back on it. A member on here had that happen, and basically his buddy was spinning the clock spring like a dimwit, and now, they had no clue of it's proper center point. When everything is back in place, battery hooked back up, airbag light should not be on, if it is, then you will have to reset it.

[bssmi]

Check the relay first, with that done, if the horn is still going nuts, then move on the the clock spring.

To access the clock spring, you take the steering wheel off. Disconnect the battery before you do so, let the car sit for 16 minutes so it can go to sleep. 2 torx screws, 25's I think, throught the slits on the rear of the steering wheel spokes. These release the airbag. With the battery disconnected, you can unplug the airbag wire and steering wheel controls. Those plugs were plugged into the clock spring. You must take the steering wheel nut off and the wheel should come out. I would check the contacts where the airbag makes contact with the wheel, make sure the springs have the connection free, maybe that's all it was. Clock spring, really no way to check it, order a new one and install it. And for God's sakes, don't let your goofy friend play with the new spring, they come with a piece of tape keeping the clock spring in place. You peel it off when you are ready to replace the steering wheel back on it. A member on here had that happen, and basically his buddy was spinning the clock spring like a dimwit, and now, they had no clue of it's proper center point. When everything is back in place, battery hooked back up, airbag light should not be on, if it is, then you will have to reset it.

Thanks a bunch! I've been looking for info on how to open the panel with the horn relay in it since reading the responses in this thread and will definitely try it once I figure out the access point. I hope that it's the relay rather than the clock spring as it sounds like a more difficult job. *fingers crossed*

[JimLev]

Move the steering column out and down.
Remove the 4 screws under the front edge of the lower panel.
There are 2 little tabs to twist 90 deg where the lower panel meets the firewall.
Remove the 2 connectors on the beeper, that will allow you to remove the lower panel.
Remove the top and bottom screws that hold the steering column plastic cover together that is behind the wheel, then split the cover open.
Next remove the wood (?) trim pieces on both sides of the steering column, then remove the screws behind those trim pieces that support the panel.
Then remove the plastic plug on the left side of the upper panel, that will reviel a screw. It's near the side air hole that blows air into the door vent.
There are probably a few more minor things needed, you'll figure it out when you start.

[bssmi]

Move the steering column out and down.
Remove the 4 screws under the front edge of the lower panel.
There are 2 little tabs to twist 90 deg where the lower panel meets the firewall.
Remove the 2 connectors on the beeper, that will allow you to remove the lower panel.
Remove the top and bottom screws that hold the steering column plastic cover together that is behind the wheel, then split the cover open.
Next remove the wood (?) trim pieces on both sides of the steering column, then remove the screws behind those trim pieces that support the panel.
Then remove the plastic plug on the left side of the upper panel, that will reviel a screw. It's near the side air hole that blows air into the door vent.
There are probably a few more minor things needed, you'll figure it out when you start.

Thank you very much for the instructions!