Horn won't stop blaring

I don't know why you are looking at drains and computers- if the horn won't turn off, it is usually the horn button on the steering wheel- that switch gets a lot of use and is the first thing to look at- in the meantime, find the horns under the fenders and just disconnect the wires from them- it should be easy and you can at least drive the car until you can get somebody to repair that horn switch-

Jamnblues the horn was disconnected but still caused a battery drain down to 8volts within 4 hours. Water has backed up during heavy rain in the clogged water drainage pan which sits on the passengers side (Australian model) under the wipers and run down into the passengers side floor and in the dash. We're wondering if water has tracked down throughout the PJB or other parts of the dash... And if so what could be causing this problem now that the water seems to have dried out . The night we had the heavy rain and the water ran into the car and the horn went off, the alarm wouldn't stop even though we turned the key in the door and started the truck. Also, even after turning the truck off the rear window wiper would still turn on(one time only) and the fans kept working on the dash( one time only) ...along with several other weird things happening like the Speedo going to 200klm and the tacho to 8000rpm. It seemed to us that a good bit of water had made its way in somewhere... But now it's proving difficult to isolate the cause of the issue so we can fix the problem.

Further.... This has happened before which is why I think the previous owner sold us the truck. I don't think she realised that the water was getting into the passengers side due to a clogged drain. She told us that she had left the sunroof open. If she had just been honest we could have fixed the problem. Anyhow, we're also suspecting possible corrosion??? Also,is it possible that the water Had tracked down into the GEM? IDK