Burned by the Explorer

Jul 07, 2012

RAY: This was sent in by Dave Satterfield. He writes:
It was an early fall evening when my wife drove our 1994 Ford Explorer about three blocks from home when it started making a great screaming noise and smoke was coming from under the hood.
My wife turned off the car and called me for help. I was home in my jammies but I  got in my car nonetheless and drove over there. Being the guy, I was obliged to open the hood and I tried to look for something wrong even though it was a dark and stormy night.
On a hunch I reached in and touched something that should have been cool but instead I got a second-degree burn on my finger.  Wounded and whimpering, I walked home while my wife continued her trip in my car! She left the Explorer smoking and smoldering by the roadside.
After getting ice on my finger, the pain subsided enough so that I could think straight. I walked back to the Explorer, adjusted something on the dashboard, started it up and drove it home with no problem.
What did I do?  And what was wrong with the car?

RAY: Here's the answer. He turned off the defroster. What was wrong is that the air conditioner compressor had seized.
Most modern cars now have one belt that runs everything. The air conditioner pulley is turning all the time whether the air conditioner is on or off. But when you turn the air conditioner on, you engage a magnetic clutch which makes that pulley that is spinning via the belt, turn the compressor. But if the compressor is seized the pulley can no longer turn and the belt will begin to screech and slip around that pulley and cause smoke and heat and eventually fire!
But if you turn off the air conditioner, that compressor pulley will go back to free wheeling because the magnetic clutch is disengaged. And the reason that thing was hot enough to burn his finger is that the defroster was on. As soon as he turned off the defroster, all was fine.
We'd also accept turning off the air conditioner as an answer. But since it was a dark and stormy night on a fall evening, the defroster seemed like the more appropriate answer.  Do we have a winner?
TOM: Yes we do. The winner is David Sternberg from Chittenden, Vermont. Congratulations, David!

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