Dear Tom and Ray:

There's something that's been bothering me over the last several years, but you must not laugh. At night when I'm driving around in my '93 T-Bird, street lights sometimes go out as I pass. This seems to happen every five minutes or so. When I told my wife, she thought I was nuts. She came along for ride so she could ridicule me. Well hi-dee-ho; she was all freaked out because it happened three times over several miles. We then went to pick up the kids and went to Dairy Queen. And as we pulled up to order, the whole building went dark (I can get sworn statements that this happened!). Can you explain these weird events? -- Gary

Ray: Of course we can explain these events, Gary. Most street lights these days are high-pressure sodium fixtures. And the flickering is a sign that the bulb needs to be changed.

Tom: Most household light bulbs fail completely when they wear out. But when the tungsten in the street light is failing and can't keep the lamp hot enough, or the sodium gas is slowly escaping and there isn't enough pressure, the street light shuts off, but then continually tries to restart itself. And when conditions are "borderline," you'll see a lamp on sometimes and off sometimes. The closer it gets to complete failure, the more frequently it cycles on and off.

Ray: So the cycling bulbs are a sign to the local electrical department that it's time to change the bulb.

Tom: The old mercury vapor lamps that they used to use didn't do this. They just got dimmer and dimmer. And the problem with that was that it happened so gradually that nobody noticed until they couldn't see anymore. "Fred, didn't we used to be able see on this street at night?"

Ray: As for the Dairy Queen, my guess is that they were closing. Did you notice that all the workers went home and said goodnight after the lights went out? That would be your hint, Gary.

Changing your oil regularly is the cheapest insurance you can buy for your car, but how often should you change it? Find out by ordering Tom and Ray's pamphlet "Ten Ways You May Be Ruining Your Car Without Even Knowing It!" To order, send (check or money order) to Ruin, P.O. Box 536475, Orlando, FL 32853-6475. You can also order online.

© 1998 by Tom and Ray Magliozzi and Doug Berman Distributed by King Features Syndicate, Inc.

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