QDear Tom and Ray:

I have run into a problem with my 1993 Jeep Cherokee Sport. Something is causing the fuse that serves the power door locks, radio, cigar lighter and dome light to blow. You put in a new fuse, and it blows before you can even test things out. Just before this started, the power locks were acting up -- sometimes they would work, and sometimes not. Could the power-lock switch or actuators cause this? Is it going to be a matter of replacing the locks, or can this be fixed without buying an all-new set? -- Matt

ATOM: This is going to be a pain, Matt. Fortunately, at least you've got a good type of short to deal with.

RAY: Right. You've got a dead short, which means it's not intermittent -- it blows the fuse immediately when you replace it. That makes it easier to find.

TOM: The way to find a dead short is, first, buy a lot of replacement fuses. Then start disconnecting one suspected electrical component at a time. After you've disconnected a component, replace the fuse. If it doesn't blow, you've hit pay dirt.

RAY: Approach it logically. You know it's either the locks, the radio, the lighter or the dome light. I'd start by eliminating the radio. Radios almost never blow fuses, in my experience. So now you're down to three possibilities.

TOM: I'd disconnect the lighter next. You can remove the wire from the back. That's easy to do, and lighters frequently cause problems.

RAY: When that's not it, Matt, go for the dome light next. That pulls down from the headliner. Once it's pulled down, the wires should be exposed. That's easy, too.

TOM: And when you've eliminated everything else, you then have to tackle the door locks. That's not so easy.

RAY: Start by opening the door and looking at the area where the hinges are. You'll see a sheaf of wires that exit the A-Pillar (the front of the door frame) and enter the door itself. Since those wires get bent every time the driver's door opens and closes, that's where you're most likely to get a fraying or broken wire that's touching metal or another broken wire. So, look there first and see if you can find any evidence of exposed wiring. If you do, fix it, and then test it.

TOM: If you don't find a problem there, then you're going to have to remove the inside door panel. It's held on by about 1,400 little clips. Try not to lose more than 1,300 of them, or it'll be hard to get the door panel back on.

RAY: You can then try disconnecting the door-lock switch. If the fuse still blows, try the actuator itself. Once you get that fuse not to blow, you're in business, Matt.

Dear Tom and Ray:

I have a '96 Ford Windstar. When I go to the convenience store in the winter, my wife and daughter usually wait in the car. Because it's cold out, I leave the heater on for them. One time, my father-in-law was waiting in the car with them. It was nighttime, so not only did I leave the car running, but I left the headlights on. When I came out, I got a speech from him about how leaving the lights on when the car is only idling will greatly shorten the life of the battery. Is he right? -- Eric

TOM: Virtually all modern charging systems are equipped to run the headlights without using any electricity from the battery. The engine will use a tiny bit more gas because the alternator is working a little harder. But it's practically immeasurable. So, when the old man is around, do him the kindness of turning off the headlights when you're parking in idle. It'll make him feel useful and respected.

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(c)2005 by Tom and Ray Magliozzi

and Doug Berman