Crusty and the Cruise Control Conundrum

Jan 28, 2008

RAY: This was sent in by a listener named Oscar Palmquist and I did have to change it around a little bit. In fact, if I hadn't mentioned his name, he wouldn't have recognized it!

Oscar writes, "A customer was in the shop one day with his camper van. It was one of those old Chevies or Dodges, I don't remember exactly what it was, but one of those kinds of things. And his complaint was simple. His cruise control was malfunctioning. When driven on the highway, it would drop out of cruise and have to be reset, sometimes several times per mile. What a pain! If there were bumps in the road, it was at its worst.

"Now the mechanic was convinced it was a loose connection, possibly a bad ground. So he jacked up the rear end to get the two drive wheels off the ground, started the engine, put the thing in gear, and set the cruise control. He then began to test every connector by shaking and pulling every plug and wiring harness. No luck. He banged on the dash board, jostled the cruise control switch, even changed the angle of the tilt wheel, checked for ground connections, did all that stuff. No luck.

"After half an hour he was getting frustrated. From the inky shadows of the lunch room, Crusty emerged, having just finished his sixth Bavarian Creme donut of the morning. He stood there, coffee cup in hand, his gaze fixed on the rear of this van. He mumbled, 'The lights, the lights.' We didn't pay attention.

"Five minutes later he still hadn't moved. And still he mumbled, 'The lights. The lights. The solution is in those lights.'"

And he was right! What did he see in those lights on the rear of that van that gave him the essential clue?
RAY: Crusty noticed that the red plastic lenses for the brake and taillights were slightly deformed, and what had caused that was excessive heat. His customer's brake-light switch was faulty, and with little or no provocation the switch would get activated or closed, and turned the brake lights on.

And when it did that the cruise control would think the brakes were on, just like it's supposed to, when you step on the brake the cruise control shuts off. So if those brake lights were staying on most of the time because of this faulty switch, that would cause these plastic lenses to soften, and deform. So who's our winner?

TOM: The winner is Mary Middleton of Pueblo, Colorado. And for having her answer selected at random from among the pile of correct answers that we got, Mary's going to get a 26-dollar gift certificate to the Shameless Commerce Division at, with which she can get her very own Car Talk football shirt, perfect for catching pretzel crumbs and absorbing beverage spills while you watch the game. Congratulations Mary!

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