Article #8 Just a broken switch, but kinda a big deal

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Adam Bahret
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Fortunately, not all failures in a UC7 are fantastically dramatic, like having gas cans for a back bumper and wondering what would happen in a fender bender. However, we have to remember that even the smallest of failures can mean big problems. It doesn’t take much to ruin the customer experience.

My Carrera UC7 exercise has just demonstrated exactly what I hoped I would find. It’s not earth-shattering by any means or even difficult to root cause, but it is a perfect little gem to improve product development which is one of the primary objectives of UC7.

The most excitement this failure mode would bring is at a rushed airport pickup; my Carrera has a broken trunk release switch. I have to say, it’s a peculiar failure for a car with 28,000 miles on it, especially when the first 25,000 miles were ridiculously pampered.



Now, when I say ridiculously pampered, I mean ridiculous.  This car is 15 years old and, when I received it, had only 25,000 miles on it. That’s an average of 34 miles a week for its entire life. Basically, If you only used it to go into town to get coffee on Sundays that’s about how many miles you would accumulate over 15 years.

The wonderful lady I bought this car from would be absolutely horrified if she knew what was happening to her baby.  I think she actually called it “her little girl,” good grief!  This is how pampered its life was; It was stored in a climate-controlled garage. She lived in Texas and the closest Porsche dealer was 3 hours away (everything is far in Texas).  When it went to the dealer IT WAS TAKEN ON A FLATBED TRUCK! She didn’t want to put the mileage on it or get chips in the paint from highway driving.

It gets better. AFTER we closed the deal, she kept checking to make sure I got an enclosed truck to carry it to Massachusetts. She was concerned about it getting dirty or wet or maybe even the breeze blowing on it too hard in an open carrier.  For God’s sake, it’s my car! I’ll have it pulled by a horse with digestive issues if I so choose.

And the coup de grâce, she put white t-shirts (that she went out and bought) over the seats in case the guy who loaded and unloaded the car was dirty from loading other cars.  I swear, I am not making any of this up.  She’ll have a heart attack if she ever finds this blog series. 

I feel that this car finding its way into my hands was no coincidence. It was an intervention from the cosmos.  What a tragedy the first fifteen years of its life was, such an amazing piece of machinery wasting away in a room kept between 65 and 78 degrees fahrenheit.

Anyway, back to the failure mode, the frunk switch (it’s called a frunk because the trunk is in front). In truth, I bet this frunk switch was actuated only ten times in its entire life before I got it.  I doubt the previous owner ever even used the car to pick up groceries or a friend from the airport.

So, was it my UC7 that broke the frunk switch in less than 3,000 miles over seven months?  The simple answer is yes, but let’s figure out what happened. The frunk release is a small lever switch that actuates an electronic button. It is located inside the door sill. If you open the driver’s door and look down you’ll see it.

So, how did I manage to break it?  Well, this car was not intended to have things loaded and unloaded from the roof.   Even so, how does that relate to a switch in the door sill?  When you want to load things onto the roof, the door sill becomes a perfectly placed stepping stool. Now, the switch is recessed so there is no direct impact on it, but what about when I use it over and over again as a step wearing work boots?

You see, that car and I wear matching shoes wherever we go. For the first few months of its life with me, it was winter. It had knobby snow tires on and I had my work/snow boots; boots with big tread that hold dirt and grim. Every time I stepped on the sill to load or unload wood or a myriad of other things, I was putting gravel, sand, and salt into the switch mechanism.  Eventually, there was enough in there to create an entirely new leverage point for the switch. This stressed the lever until the hinge point failed.

Now let me tell you why this is such a good UC7 example. It leads us to two of the golden nuggets of UC7; simple robustness improvements and input for next generation products and new product lines.

Ok, let’s put this UC7 exercise discovery where it would be if it had actually been done in the design process for this generation of Carrera. To start, I looked up when the design for this switch was first added to the 911 lineup. It turned out to be the previous generation Carrera from 1999 to 2005.  Let’s say the design period for that would have been the four or five years leading up to 1999 (1994-1998).

If the Carrera was designed in that time period and this failure mode occurred in the UC7 exercise, then there would be a report that said something like, “Frunk switch broken, Root cause: dirt/gravel in mechanism from operator’s shoes when stepping on sill.”

This would likely have led to either of the following actions being taken. The first possible option is that they would have decided to add a rubber seal so the dirt and sand couldn’t get down to the working parts of the switch or, second, they would have moved the switches to the door panel or console.  Both are simple robustness improvements, but does this matter for a non-utility vehicle?  Yes! Sports cars find their way to the beach on sunny days and are enjoyed out on open roads that snake through desert climates.  Those roads are great places to find out if that spec top speed for your car is true?

Even though it is uncommon to step on the sill in a low car when entering, it is easy to accidentally shake sand or dirt into it when your foot bumps it on the way in or out. Maybe the failure mode wouldn’t happen over the course of 3,000 miles, but even occurring at 30,000 miles this would be seen as a poor design.

Would they have found this issue in their regular use case testing?  Possibly, but they would have to have gotten lucky in testing to have enough of their other use case tests just happen to repeatedly drop debris into the switches. It’s a far more likely conclusion that a small group of customers had issues over the years and the issue simply never made it onto their radar to be correctly addressed, and may have always persisted.

What about the second benefit, the next generation and new products? From 1955 to 2002 Porsche only made sports cars and it wasn’t until 2003 that they introduced their first SUV.  As I mentioned, the frunk switch in the door sill was introduced in the Carrera in 1999, long before 2003.

I am sure there were many things they found challenging about designing an SUV for the first time. The SUV program was likely in full gear for a five-year period, from 1998 to 2003.

Would having learned about the debris vulnerability in a sill located switch in 1996 been valuable input when creating an SUV for the first time?  Absolutely, it is foolish to put anything less robust than a ladder step tread in the door sill of an SUV.  Of course, owners will be loading stuff on the roof of an SUV at regular intervals in all kinds of conditions, thus door sill = ladder step.

In summary,  they potentially would have had an interesting lesson learned from a predecessor product. Learning this lesson so early on would have mitigated the issues of finding it in prototype testing or even later, in the field after release.  In other words, before they even got to starting “best practices” they would have a “no levers, switches” in areas that can collect debris guideline.  It seems obvious to say that now, but clearly it wasn’t a guideline for their 40 years of making sports cars or I wouldn’t be writing this article.

Learning from this portion of UC7, here are some thoughts for you to consider about your own products. Have you ever found an unexpected issue with a new product line?  Was it because new functionality that was not in your wheelhouse was added? What opportunities early on might you have passed by to explore these corner use cases earlier? How well is your use case exploration and definition process formalized and constantly updated?


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