Horn blows when parked.

I have a '22 with about 44k miles on it that I've had about 4 months. This afternoon after being driven this am the horn stated blowing by itself, no input. Sitting in the garage, nothing disturbing it. Doors locked with the door switch on exiting like always. Didn't pulse like the alarm or panic mode, was steady for about 3 minutes. Keys were in my faraday box. I went out with the keys to try to stop it, none of the fob buttons made any difference, opening the door and pressing the start button without pressing the brake made no difference either. Popped the hood to go after the relay and several seconds later, it stopped. Anyone have a clue as to a possible cause? I did a search, nothing came up. TIA.

 

I've seen it all now. Vehicles are blowing themselves. Many men have tried this and failed.

 

Ha ha ha ha!

 

Does it have an aftermarket alarm system on it? Also, what kind of charge is the battery holding? The reason I ask about both of these is because I once had an Isuzu Trooper that would do similar things. What it came down to was an alarm system that was haphazardly installed (grounding), and a battery that wasn't holding a full charge. For some reason when the two mixed, weird things would happen. Not sure if one perpetuated the other, but I fixed the issues with the alarm and installed a new battery. Never had the problem again.

 

Factory alarm, battery good. Started it a bit later and cranked fine. Didn't put a tester on it, but would have passed I'm sure.

 

Just a thought, Have you checked to see if any possible rodent damage in and around the harness under the hood?

 

Good point, I've had that issue in my other garage with a different vehicle, but so far none in the house garage or on this vehicle. Yet.

 

You say it was not flashing and honking like the alarm going off? I ask because it sounds like when my alarm (full lights and all) was randomly going off. Seems to be a common issue these. Was the hood switch. I ended up by passing the hood switch to fix.

 

No lights, no pulsing horn, just blowing like a stuck horn pad/switch.

 

This happened to me once... you need a new battery. At least that was the case for my battery. One afternoon at work, when I returned to my 4runner it was just sitting in the parking lot with the horn going off (if I remember correctly). No lights, just the horn. It started just fine. At the time my 4runner was about 2.5-3 years old.

When I got the battery tested, the amps were low and apparently it was in early stages of going bad. Went straight to some auto parts store and got a new battery put in, it never happened again.

Just my 2c.