Can You Debug SUV Interior Lights?

Kenny Tilton
3 min readMar 10, 2021

“Hold out your hands,” Bob said.

“Light Bulbs” by Sworldguy

Bob was a good and trusted friend, so trusted that I had let him drop me off at my ski lodging before ferrying the rest of the crew to their lodging further down the access road in my SUV. I held out my hands.

Bob reached into both pockets of his ski parka and started pulling out little light bulbs and dumping them into my cupped hands two and three at a time.

“You could not get the interior lights to go out,” I said. “You took out all the bulbs so the battery would not die overnight.”

I knew because it had happened to me, but I am a computer programmer so I had been able to debug the case of the stubborn lights without removing them. Want to be a programmer? See if you can save the battery without removing the light bulbs.

Here is your failing sequence to debug:

  • You take the keys from Ken when he gets out at his lodging, hop in the driver’s seat of his SUV, and close the door.
  • The interior lights go off. Duh.
  • Drive the rest of the crew to your separate lodging down the mountain. Stop at the lobby entrance to unload before taking the SUV alone to the back parking lot for the night. Everybody gets out of the car. You get out, open the SUV back door, and everyone pulls out their day packs.
  • Everyone but you heads off to their rooms with their stuff after closing their doors.
  • You close the back door, hop into the driver’s seat, and close your door.
  • The interior lights stay on. Hmm.
  • You figure out we must have brushed the overhead rocker switch at the back of the SUV into the “On” position while extracting the gear.
  • You get out, walk to the back, open the back door, and toggle the overhead switch. The lights stay on. You close the back door. The lights stay on. Hmmm. That was not it.
  • You open the back door, toggle the switch back to where you found it. Of course, the damn lights stay on.
  • You close the back door, get back in the driver’s seat, and close the door, hoping for a miracle. The lights stay on.
  • You check the dashboard controls, the other interior manual switch directly overhead, nothing makes the lights go off.
  • This is 1985, you cannot call me on a cell phone, and you do not even know the name of my lodging. Twenty minutes away.
  • You start taking out light bulbs.

Full marks to Bob for his brute force solution. The SUV battery was fully charged in the morning, and it took only a few minutes to put all the light bulbs back in. But you want to be a programmer.

Q: Why could Bob not get the lights to go out? and,

Q: What did Bob decide was true that was not true?

Welcome to my world.

[Spoiler alert: solution is in the comments.]

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Kenny Tilton

Developer and student of reactive systems. Lisper. Aging lion. Some assembly required.