Q: We love our 2007 Prius, and we have 217,000 miles on it. About two months ago, I was driving at night on unlighted neighborhood streets and both of my headlights went off. I toggled the light switch off and on, and the headlights came back on. This has happened several times since.

We called several dealers and repair shops. They all said to replace the headlight bulbs. If one would go off, I would agree. But both at the same time? I would say it has to be some control that is common to both. I looked through a schematic diagram, and there are several components that are common to both headlights. The simplest one appears to be a ground to the chassis, but I'm not a mechanic, so I can't locate it. Have you heard of this problem and the fix for it?
A: Because toggling the switch brings the headlights back, it sounds like a circuit breaker is involved, but it's not the underlying cause. If there is an excessive current draw, the breaker will open. When it cools down, the circuit closes and the lights work — temporarily. By switching the lights off, you are allowing the breaker to cool. Unfortunately, I can't guess what the root cause is, so you will have to have a technician troubleshoot it.

A guarded response

Q: Are mud guards worth it on new cars? Do they prevent rust on the body behind the wheels? Do they reduce the miles per gallon?
A: Mud guards do not affect fuel economy or reduce rust. They do, however, keep mud off the fenders and sometimes the rocker panels, so you may be less likely to soil your jeans getting out.

The dark side

Q: I'd like to respond to a recent question about transition glass in windshields. I was a licensed optician for almost 40 years, so I can cite several issues. Transitions always have a slight residual tint. They darken fairly quick, but take about four times longer to lighten. Enter a tunnel and you'd probably be all the way through it before the windshield lightened. They are temperature-sensitive and don't work as well in hot weather. And finally cost — transition lenses have millions of silver halide crystals in them. Detroit loves to save pennies, not spend hundreds.
A: Your response is an eye-opener. (Sorry, couldn't resist another pun.)


Q: In your recent reply regarding a plugged drain tube, you indicated that the B pillar is between the windshield and door frame. That would be the A pillar.
A: I might try making up some excuses, but the only one that holds water (yes, another pun) is that I goofed. Thanks for keeping me on my toes.

Bob Weber is a writer, mechanic and ASE-certified Master Automobile Technician. His writing has appeared in automotive trade publications, Consumer Guide and Consumers Digest. Send automotive questions along with name and town to motormouth.tribune@gmail.com.