One problem related to horn assembly has been reported for the 2006 Ford F-550. The most recently reported issues are listed below.
My truck was parked for an hour and a half in 55 degree raining weather. I was unloading my show horses and had my three dogs in the cab of the truck. Suddenly someone alerted me that the cab was filled with smoke. We were able to get the three dogs out. They had to be treated for smoke inhalation via hyperbaric chamber treatment. Unfortunately one dog died 24 hours later due to brain damage from lack of oxygen. According to the fire department, my car seat heater malfunctioned and ignited. My car seat was part of the longhorn king ranch custom interior that Ford had installed before selling me the truck. Please feel free to contact me if I can provide any more information.