This one has stumped a number of car shops and...

Dear Car Talk

Dear Car Talk | Jul 01, 2002

Dear Tom and Ray:

This one has stumped a number of car shops, and it has a funny element to it. About a month ago, my wife was backing our 1997 Mercury Sable out of the driveway. As soon as she put it in Reverse, the radio cut off. As soon as the automatic transmission was shifted into any other gear, the radio came back on. My first reaction was: "This is a new safety device. Somehow, the car figured out how to tell when my wife is behind the wheel and, given her general difficulties driving a car in Reverse, wanted to eliminate all possible distractions." Unfortunately, the car isn't that smart, and it does it when either of us is driving. Do you experts have any idea what would cause this? -- Ted

RAY: Well, I'm going to guess that it's very cold and damp in your garage, Ted. And if I were you, I'd start by installing some sort of heating system.

TOM: You think the cold and dampness in his garage is causing his radio to cut out?

RAY: No. But after his wife sees that nasty comment he made, he's going to be sleeping there, so he might as well make it comfortable.

TOM: Truthfully, Ted, this is not a problem we can solve for you via the newspaper. It's a problem that a mechanic has to investigate in person. There's no direct connection between the back-up lights, for instance, and the radio. But we can give you a few suggestions about where to look.

RAY: One item to check is the ignition switch. Sometimes, if an ignition switch is worn out and isn't staying exactly in the "run" position, you can lose accessories. Why it would happen only in Reverse, I don't know, but the shift lever is in that same general area. So when the car is in Reverse and the radio cuts out, try gently moving the ignition key around and see if you can get the radio to come back. If you can, my money is on the switch.

TOM: Another consideration is that the whole engine shifts when you put the car in gear. It moves in one direction when you put the car in Drive, and in exactly the opposite direction when you put it in Reverse. It's possible that when you shift into Reverse and the engine moves, it might tug on a ground wire or stretch a connection somewhere. This condition would be made worse if you have a worn motor mount (the large rubber insulators that are supposed to hold the engine in place). And we replace lots of motor mounts on these cars.

RAY: It could also be a loose wiring harness at the fire wall, or any number of things that we can't identify for you now (we'd have to take over this whole section of the newspaper to list all of the possibilities). But with the car in front of him, a mechanic ought to be able to figure this out pretty easily. He'll check the ignition switch and start jiggling wires until he makes the radio cut out, and then he'll know exactly where the problem is.

TOM: Meanwhile, don't forget to make sure your garage door is shut all the way before you go to sleep, Ted. It not only gets drafty, but when the raccoons climb on top of you in the middle of the night, it'll scare the hell out of you.

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