1998 Ford F-150A new lawsuit has been filed that blames a woman's death on a defective Texas Instruments cruise-control switch inside her 1996 Ford F-150. Darletta Mohlis died in a house fire in May while her truck was parked inside her garage. Ford claims the fire started elsewhere and that the truck was not the cause. Where the lawsuit gets a bit absurd is that DuPont has also been named, as they supplied raw materials (Kapton and Teflon) for the switch.


I understand that it?s typical to name every party that may have some vested interest when filing such a lawsuit, but it?s highly unlikely that DuPont will be found liable. What is likely is that they?ll burn through hundreds of thousands of dollars in the process of defending themselves, which doesn?t seem like a good use of their resources.

TI?s liability (assuming the switch was at fault) is a more difficult question, as Tier 1 suppliers (who ship directly to the OEM) are usually deeply involved in the design and validation process. If Ford under-specified the switch and TI met the inadequate specifications, then the burden should fall on Ford?s shoulders. On the other hand, it?s possible the TI delivered a part that did not meet all of the requirements, in which case they will feel some pain. 

Some investigative reporting by WXYZ, the ABC affiliate in Detroit, includes an interview by a TI representative that pins the blame on Ford?s usage of the switch (of course). The fact that TI has paid out millions of dollars in out-of-court settlements, usually after being called into court by Ford as a third-party defendant, would seem to imply that TI is at fault. The failure mode - brake fluid enters the switch from the master cylinder, causing a short that ignites a fire - certainly seems to be a result of a switch design flaw. TI, however, claims that Ford powered the switch from a 15-amp circuit but specified it for only 1 amp, and additionally powered the switch from a Hot At All Time feed (instead of a switched ignition circuit) that left the vehicle vulnerable to the failure even once the ignition was switched off and the owner had walked away. The contention here is that while TI built a defective product, Ford applied it in such a manner that turned a benign failure into a catastrophic one.

The bottom line is that there?s been property damage and loss of life due to what was probably regarded at the time as a simple component in a well-developed subsystem. It goes to show the difficulty in producing a large number of complex and safe vehicles when cost is such a critical parameter. Sometime, sweating the details means more than making a rattle-free piece of interior trim.