Horn blows three times

[jpmss]

I just bought a 1999 Explorer Sport and been having a problem. when I get in and turn the key on after about 30 to 40 seconds the horn will blow three times. my dealer can't figure it out and thinks its an after market safety device that has been installed but I don't see anything. does anyone have any ideas its annoying having the horn blow every time get in and start the Explorer.

 

[410Fortune]

wow that is odd.
3 times = sounds like some sort of alarm was installed for sure.

the 99 is equipped with PATS so your key has a decoder in it or chip or whatever.

I would not accept the answer that they dont know why, they are a Ford dealer they should be able to diagnose an issue with a Ford horn, aftermarket or not.
Aftermarket security devices do not sound a horn after the truck is running.

this might be the strangest problem I have ever heard on this forum
CONGRATS!

 

[MONMIX]

Hmmmmmmmmmm.
Very, very odd.

The most I can speculate is a short some where.

 

[whoathere]

you'd think a short would cause it to happen more then just when the car has been on for 30 to 40 seconds, but you can't rule that out. Does it only do it when the engine is running, say you turn the key to the on position will it do the same thing after the same time?