Why does the horn honk randomly? Because GM...

This is my son's 2010 Chevy HHR...well, it's mine but he drives it as his daily.  Very recently the horn suddenly started going off randomly while he was driving.  No rhyme or reason.  He would be driving and then suddenly it would honk for 10-15 seconds and then stop.  It'd be fine for 10 minutes and do it again.  I told him to pull the fuse until we could get a better look at it.  Now the horn won't honk when you press it...however it honks when you turn the key to start it.  Every. Single. Time.  It's at the shop now getting fixed, as I don't have time to screw with it.  Thoughts on what on earth it is?  Only a GM would do this stuff...the car runs fabulously but this is just strange.

Are there steering wheel controls?  Are they working correctly?  If not working correctly it would support my theory that the honking is caused by a bad clock spring.  

My dad bought a new Chevy W/T1500 in 1995.  It would honk the horn when you started it unless you put the left turn signal on when you turned the key.  They said it was a theft deterrent.  Dumbest GM thing ever.

Clockspring. My GMT800 Yukon Denali had weird horn issues that were caused by the clockspring wearing out at a whopping 130k miles.

So the shop just called.  The horn honking when you turn the key was caused by someone putting a jumper from the horn relay to the ignition.  WTF????  Definitely need to ask my son about that.  But the mystery of why it honked randomly while driving is unsolved.  I'll ask them about the clockspring.  Car only has about 91k miles.

In reply to SKJSS (formerly Klayfish) :

Some sort of prank perhaps. I've heard of people jumpering the horn to other things, like brake lights, so that any time someone hit the brakes their horn honked.

On 90s-2000s Porsches this usually means that the little rubber bushings that hold the airbag off the horn contact have perished, but it works like the horn being connected to the brake lights...

In reply to SKJSS (formerly Klayfish) :

Remove the jumper and see if the random honking stops.

One day while I was trying to figure out how to keep my nitrous setup inconspicuous, I got the idea of using the horn button to activate the nitrous. All the work is done, you just disconnect the horn, and plug the spade connector up to your nitrous relay. It worked so well I used the horn button on every car after that.

Would not have been great on a Fairmont.

Someone has been watching too many old Top Gears where they always prank James May. 

I had a '95 LeSabre that started to do that on cold days.  It would go off when turning.  Never fixed it, just pulled the wires off both horns (one in each fender).