Wow, what was I thniking when I hit send before reading the original post.... I've tried to fix the bad grammar below. Sorry.
Ford built (and still builds I think) vehicles were there was constant power to a circuit that included a brake fluid pressure switch. This switch is a last ditch safety device that will disable the cruise control if you press on the brake. Some of these switches were defective and leaked slowly. Because of the contamination of the contacts the contact resistance built up to the point that even a minor current flow generated a temperature high enough to ignite brake fluid. The small brake fluid fire that broke out would sometimes ignite other flammable material and a significant fire sometimes ensued. Fires from this failure almost always occurred when the vehicle was unoccupied. When the problem was first discovered it was assumed to apply to a relatively limited range of F150s and Expeditions. There were very few reports of fires and they were all within a well defined group. Ford initiated a recall of the affected vehicles. However, after word of the problem got out, all sorts of Fords, some with completely different style switches and circuits, started bursting into flame. Once bottom feeding trial lawyer got into the act, Ford was screwed. Ford first widened the recall to all F150s and Expeditions with the type of circuit associated with the original problem. Now they have expanded the recall to cover pretty much any Ford that uses the brake pressure switch.
I've owned two Ford with the "dangerous" switch. I never worried about either. In fact, the switch was overkill. It was itself an over reaction to lawsuits that claimed cruise control systems went wild causing cars to go out of control.
The bottom line is - there are definitely fires that Ford has admitted were caused by cruise control deactivation switches while the vehicle was parked and not running. In fact, this was the usual failure mode. See:
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Ed