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Wednesday, September 07, 2005

Massive Ford Recall (Ouch)

The Reuters news service reports that Ford is recalling 4,000,000 trucks, built between 1994 and 2002 to repair the cruise control deactivation switch. This switch is under NHTSA investigation for underhood fires. The theory for the switch failure is that the brake fluid may be ignited by the switch, which his always hot, if the internal seal fails.

I applaud Ford for doing the right thing, but you can almost hear Ford's investors, dealers, and customers collectively wince, "here we go again".

6 comments:

Shawn said...

This is a very interesting case in terms of failure analysis. No one really knows why these seals fail. If it was random, you can say that statistically some seals fail. However, for some reason no one is sure of, it is much more likely to happen to some models but not others that are using the exact same part.

Very strange.

Ford is doing the right thing. Take this thing out of the equation completely.

Ray said...

As we electrical engineers know, "Off" isn't really "Off" any more for cars or other electrical stuff which needs some juice to keep its computers and other things idling when not in service.

What's the solution on this one? Will moving the B+ hot wire over onto the other side of the key switch do it or will they put in a better pressure switch on the master cylinder to deactivate the cruise control.

The Auto Profit should know!

The Auto Prophet said...

In fact I have read that the fix is a fuse which will pop if high current is detected flowing through the switch.

Which means the failure mode will shop up either as cruise control that won't go on, or it won't go off.

The Angry Engineer said...

If I'm not mistaken, the switch in question is redundant. It's in series with the mechanical switch that's mounted on the brake pedal. If either switch is open, or if power is cut (say, due to a blown fuse), the cruise control system should deactivate. Ironic that a redundant safety feature should be the part that causes the problem, eh? Most other manufacturers use a single cruise switch. Most other manufacturers also are smart enough to put such a load on a switched battery circuit, and to properly fuse such a switch. Putting a 1A switch on an unfused circuit is not smart engineering. Would anyone install such a circuit in their house?

I've got no sympathy for Ford with this one. They're not "doing the right thing". The right thing would have been to do some relatively simple engineering analysis when it was found that the switches had the potential to fail and cause a fire, and then recall every single vehicle that could have burned up when left unattended. That could have resulted in a massive recall six years ago (when the Crown Vics were first recalled for this problem), and it would all be a distant, albeit bad, memory by now. But no, they decided to piecemeal this recall based on statistical failure rates, which by its very nature is a reactive process.

This is exactly the sort of crap that puts the "angry" into Angry Engineer, and is why I'm occasionally ashamed to be part of this industry.

Ray said...

Thanks Angry/Prophet:

My old Chevy had a vacuum and an electrical shut off on the cruise providing both redundancy and diversity.
Fault trees, fuse coordination curves and damage curves were my bread and butter but must be scarce in the auto industry.

The Angry Engineer said...

Ray,

Ah, yea, the ol' vacuum switch for the older cruise systems. I had forgotten about those, since everything in my fleet now has electronic cruise. I do not miss the vacuum systems ;)