Dear Tom and Ray:
Does driving a vehicle with the headlights on appreciably shorten the life of the battery and/ or alternator? I am asking about additional hours logged during daylight hours. Even though it's safer, I think many people are reluctant to turn on their headlights during a storm or at dusk because they think it is harmful to the battery. Is it? - FloraTOM: Using your headlights while you're driving doesn't affect the battery at all. Once the car is running, electricity is produced by the alternator, and the battery is really out of the loop. And while using the headlights does make the alternator work a little harder, the difference isn't enough to worry about.
RAY: There are a couple of very minor trade-offs. The headlight bulbs themselves have only so many hours in them, so you will use up the bulbs a little faster. You will also get a very slight decrease in mileage, since producing more electricity requires you to use more gasoline.
TOM: But the costs are so small that they're not even worth considering. What you're getting is increased safety. Remember, the purpose of having your lights on at dawn or dusk is not so YOU can see better. It's so other drivers can see YOU - and not crash into you. Anytime there isn't clear daylight, it's a good idea to have your headlights on.
RAY: Having said all that, Flora, I'm not sure I agree with your assumptions about why people don't use their headlights more. I think they're just afraid they'll forget to turn them OFF. Now THAT will definitely harm your battery!
Dear Tom and Ray:
I have a 1955 Rolls-Royce which was modified with a 1972 Buick engine and transmission several years ago. I drive it only occasionally. Recently, it developed a problem of seeming to "cut off" the electrical power to the engine for a moment every three or four minutes while driving. Both the lights and engine completely lose power. If driven several miles, the battery is discharged. Your diagnosis? - Floyd
TOM: Whatsa matter, Floyd, the Rolls-Royce dealer won't let you anywhere near his shop? Does he come out chasing you with his umbrella when you try to drive into the parking lot?
RAY: Luckily, it shouldn't take a Rolls-Royce mechanic to fix this, Floyd. Start by checking all of the obvious stuff - the connections to the battery and starter, the output of the alternator and the fusible links. While the car is running, you should also jiggle all of the wires that run from the positive terminal of the battery. That will tell you if the problem is a bad wire. If you don't find your problem there, my guess is that you're missing a crucial ground connection from the frame of the car to the engine block.
TOM: The good news is that you don't have to find a bad ground to repair it. You can simply "break new ground," as they say, by running a new wire from anywhere on the block to anywhere on the frame. Just to be on the safe side, I'd also replace the ground that runs from the frame to the negative terminal of battery.
RAY: And just for added insurance with this strange hybrid, Floyd, I'd try to find a Buick mechanic named Nigel or Trevor.
Got a question about cars? Write to Click and Clack Talk Cars c/o King Features Syndicate, 235 East 45th Street, New York, N.Y. 10017.