I just sold my truck yesterday and it had an AstroStart 2-way on it. The guy was filling up yesterday and left the key turned to the accessory position while filling up. Got in, started the truck and the horn wouldn't shut off, even after starting the truck. He ended up pulling the fuse for the horn relay. Any ideas/thoughts?

The horn was constant, not a beep beep beep like when you hit the panic button.