Why Does Water Collect Inside My Car's Headlights?

Q: My headlights are always collecting water inside. The dealer says he can replace them, but they’re very expensive, and he wouldn’t guarantee that the new headlights wouldn’t collect water also. I took out the headlamp assemblies and coated all of the seams between the clear lens and the back with bathtub caulk, and gooped up the rubber dingus that goes over the headlight wires with a lot more caulk, but it didn’t help a bit.

A: Let’s examine why there is water inside the lamp assemblies in the first place. As the outside temperature goes down and your nice warm headlamps cool off (either from being in the sun or just from being turned on), cooler, moister outside air trickles into the housings. The housings are vented top and bottom to allow for pressure differences, or they would quickly crack and fail. When the clear plastic lens is even a little bit cooler than the air inside the housing, droplets of moisture will condense on the inside of the lens. That’s normal. When the outside temperatures come back up in the morning, the moisture will evaporate.

Some vehicles don’t vent as well as others. Some drivers keep their cars parked in shady, damp areas or in cool, damp underground parking structures. And the moisture collects not as tiny droplets of mist but as what looks more like raindrops, and can even run down the glass and pool inside the housing.

Check to see if there’s a Technical Service Bulletin for your make and model of vehicle. If so, there may be a retrofit housing or an upgrade to the venting system. If not, you’re on your own. The first thing to try, if all you have is droplets, is to leave your headlights on while driving for a couple of hours, forcing the moisture off. If you have a spoonful or more splashing around, you may need to remove the housing and dry it out. Pour off the excess water, then add a few ounces of rubbing alcohol to the housing, sloshing it around and pouring it out. Repeat. Let the housing dry for a couple of hours in the sun or inside a nice warm house, preferably in some air that’s moving. Check that any vents aren’t plugged with spider eggs or mud. Install the housing and try to park facing south.

My Car's Battery Goes Dead

Q: Our 1999 Ford Taurus, which resides under a cover, almost always has a dead battery after it sits for a month. I have had to replace it three times in the past seven years. I tried one of those solar panels plugged into the cigarette lighter by having a clear plastic window installed in the cover. The plastic housing on the charger actually melted when the heat outside got to 118 F and shorted, further draining the battery. Who knows what the temperature got to inside the car? Sure, I can disconnect and reconnect the battery, but for what that takes I can jump-start it with a portable jump-start battery device easier. Any advice to keep the battery from dying? The car’s parked in a lot across the street from the house, so running an extension cord to a trickle charger isn’t an option.

A: Melted the solar charger? Man, I bet you could bake cookies in there on a sunny day.

Letting any battery discharge that deeply will damage it immediately, which explains your high failure rate. And the heat will make the battery self-discharge even faster than normal.

My best suggestion: Get a battery disconnect switch, wired into the ground cable. This won’t prevent normal self-discharging, but it will eliminate any parasitic drains (like the radio presets and computer memory) that are killing the battery between uses. Then whenever you need the car, all you have to do is open the hood, turn the switch on, and start it up and drive away with clean hands. A decent battery should have enough juice left after a month to light the fires. In case the idle period is a little longer, keep an auxiliary starter box in the house on a charger. You can probably get enough charge into the nearly dead battery by plugging one of these gadgets into the cigarette lighter, also leaving you with clean hands.

A second suggestion would be to hard-mount the solar charger on the front license-plate bracket and leave it uncovered by your car cover. Park the car pointing southwest toward the afternoon sun to catch the most rays.

Would The Prius Get Better Gas Mileage If It Weighed Less? Part 2

Q: I read your answer concerning "Would The Prius Get Better Gas Mileage If It Weighed Less?". It was very interesting and I agree with your discussion but I'd like you to go a step further. The thing that is confusing about hybrids has to do with their efficiency. It seems to me that using an internal combustion engine to charge the batteries which power the electric motors that move the car would be less efficient that moving the same car with the internal combustion engine. I recall someone's theory having to do with "Conservation of Energy". Applying the same technologies that maximizes the efficiency of the gas engine as a "charger" could also make it a better "mover". Right?

A: You are correct, charging the batteries onboard with an IC engine and then powering the wheels with an electric motor is inherently less efficient than just gearing the IC engine to the wheels. That’s why most hybrids have some way of doing either or both.

Two compelling reasons to use batteries:

In a conventional hybrid, the batteries are on board to capture energy during regenerative braking, using this energy (normally wasted as heat in the brakes) to accelerate the car later.

In a plug-in hybrid, the batteries are recharged by the grid. A PHEV, if driven for short enough distances to not drain the batteries, may never consume gasoline.

Would The Prius Get Better Gas Mileage If It Weighed Less? Part1

Q: I have an idea for a story in your magazine. I was thinking you guys could buy a Prius and pull the batteries and anything at all related to the hybrid portion of the car. Obviously this adds up to a lot of weight—dead weight on the interstate where many people do most of their driving. No doubt this car would then get much better highway mileage. If they built it that way, it would be much cheaper and have a much smaller “carbon footprint” due to much less energy being used to build it. As the car is now, it often has to recharge the battery pack on the highway, hurting its real mileage, not to mention the burden of all that dead weight.

A: Your logic is faulty. Here’s why:

1. Overall weight has virtually no effect on steady-state cruising economy. Fuel consumption at expressway speeds on level ground is determined largely by aerodynamic drag and other parasitic drags such as the tire’s rolling resistance.

2. The onboard battery pack is charged, for the most part, when the vehicle slows down, capturing the energy that otherwise would be dissipated as heat in the brakes. It normally doesn’t get charged during steady-state driving or acceleration. (One exception: On some hybrids, notably Toyotas, the battery will be charged to load the engine when the engine is otherwise running to warm up or provide cabin heat. This avoids wasting the fuel needed to keep the engine running when the car isn’t moving. Clever.)

3. Aerodynamic drag goes up with the square of speed, but the power needed to overcome drag goes up with the cube of speed. It takes eight times as much power—or fuel—to go a constant 60 mph as it does to go 30 mph.

That’s why the Prius, the Insight and other hybrids can actually achieve better miles per gallon during moderatespeed urban stop-and-go driving than on long, high-speed freeway trips.

How To Fix a Car Paint Scratch

New Car + Parking Lot = Scratches and Chips

It's a fact of life. Other ­people often don't treat your car's paint with much consideration. Ditto for kids and pets, not to mention the odd troll with an attitude and a set of car keys. Respraying a car can cost thousands of dollars, while respraying a single panel may leave you with a clown car that doesn't match color left to right.

Fortunately, many small nicks, scratches and imperfections can be easily retouched. A careful job is unobtrusive and may well be almost totally invisible.

Proper conditions: Be comfortable

Before you break out your touchup tools, figure out what you're dealing with. If the scratch appears thin and white, it probably hasn't penetrated through the clear coat.

If it is body-colored or shows metal, you've got a deeper problem. Regardless, never try to touch up paint unless the temperature in your work area is shirt-sleeve- comfortable for you. The paint won't adhere, dry properly or gloss up. The ideal temperature would be in the 70s F, but 60 to 85 is acceptable. You'll need to be out of the wind and sun. Indoors is best, but a shady carport should do. The relative humidity should be less than 60 percent or so: The evaporating solvent will cool off the panel as it dries, potentially lowering the metal's temperature below the dew point and letting moisture ­condense on the surface. This is not ­conducive to good surface finish.