so last night, my car was just sitting outside and horn started going off constantly and would not shut off..I jumped in the driver seat and inserted the key in the ignition and it stopped. Took the key out and it started again, then I started the car and it stopped. Took the key out and it went off again and nothing was making it stop. I disconnected the battery and it finally turned off.

What is going on here? Is a short or something ? We had a lot of rain here in Sacramento yesterday and my wife drove over a puddle of water, but I don't think it was that bad.

 

The alarm senses hood, doors & trunk.

Could be battery going bad, and thinking there is something opening and activating the alarm. moisture or a sensor going bad are other common factors.

I had this issue last year, it ended up being the plunger under the hood not being fully depressed. Ended up putting a small spacer under it and it cured my problem.

 

it's not really the alarm going off..the horn is on non-stop..battery was changed back in June. =(

 

Yikes, I got nothin then. Good luck.

 

My horn did this a year or two ago while I was driving. Pretty sure everyone hated me, lol. Eventually it went off, but they replaced something to fix it.

 

This happened to me. It was the stupid azz hood sensor. I disconnected it and it never ever happened again. I can't find a pic but if you are standing facing the open hood, it's on your left, the highest little part with a rubber boot. I have had no issues with it unplugged. No codes or warning lights either.

 

so I let the car sit for 2 days..connected the battery and tested everything out and everything was fine..later that night the horn started going off again..disconnected the battery again..the next day I pulled the horn relay out and now its ok. idk if this is ok for the long run or not lol

 

You took the relay out? Does that mean your horn isn't working? I wouldn't run around without a horn. That could be dangerous. You should try the hood sensor.

 

yes the horn relay, it doesn't work now. My car has a hood sensor?

 

Do a google image search on "G35 Hood Sensor" You should hook your relay back up and disconnect the sensor. That should stop your horn from beeping and still allow you to use your horn regularly. If I remember correctly, it is about 12 inches from the battery towards the front of the car. It has a big clip to disconnect it.

 

Yep. It looks like a plunger with a flat round top.

 

I was having the random horn alarm also. I noticed that when I would arm the system the red blinking light would never go steady for 30 seconds and then start blinking again.... It would just continuously blink.

When you lock the doors, the system runs a 30 second check, and during this check (doors, hood, and trunk, verified closed via "pins".) the light should be on continuously and not blinking. After the test is complete(approx. 30 seconds) the system arms and the light starts blinking again.

I pushed all pins in manually with the doors and hood open and armed the system successfully. I then closed the hood holding the door pins in manually and could not arm the system. Culprit... Hood pin. I deduced that the hood was not pressing the hood pin down enough to sense closure.

I stuck a felt pad onto the hood where the pin makes contact. This was enough so that when I closed the hood the pin sensed closure and was able to arm the system. Apparently because I tried to arm the system it was sensing a open hood and this was triggering a random alarm. Attached are pictures.

 

For some reason I was only able to post 1 picture. This is the picture of the felt pad on the hood.

 

SOS HELP.
Was sitting at the garage with my mechanic in process of scheduling an appointment for maintenance, when the cars horn started blaring for no reason what so ever, along with the lights flickering but no flashing like a security setting going off.
CAR WAS OFF AND UNLOCKED...
He removed the chip that controls the horn, but the AC controls kept switching between choices, the RPMs would fluctuate from 0-1k with no pressure on the gas...
Drove it home since the shop would be full till monday, but had no speedometer but my tachometer worked fine no fluctuation or studders.
IDEAS?????

 

Anyone having this problem, please file a safety report at http://www-odi.nhtsa.dot.gov. I have the same problem. Happened to me three times and yet I'm the only one the filed a report. The horns blasted long enough to burn out. Let's force a recall.