Was sitting at home yesterday when the horn on my 1999 F-350 SD starts going off, the truck was unlocked and no one had pushed the panic button on the remote. So I open the door the horn stops but as I get in I notice the blower is on and blowing with the key in my pocket I can stop the blower by simple turning it off and it has all the speeds for the fan. Shut the door and the horn starts up again. It has been raining and am wondering if the moisture has anything to do with it. Or what could have possible shorted out. Any help would be great.

 

Look for water dripping down onto the fuse panel and GEM module under the dash, left side. It is a somewhat common problem for the windshield to leak and allow water in there, causing corrosion and shorts. You may have to remove the fuse box and look at the back of it for corrosion.

 

That makes sense. I will give that a look Thanks