Question: I have heard that the federal government is going to require auto manufacturers to install an additional brake light on the rear of all cars. After having been rear-ended recently, this sounds like a good idea. Can I install such a light on my car?--J.W.
Answer: You are correct that the National Highway Traffic Safety Administration is going to require a high-mounted, rear brake light on all new cars sold in the United States after Sept. 1.
General Motors already has begun equipping its 1985 Cadillac De Villes and Fleetwoods with the lights as standard equipment. GM is also leading the way by offering the safety devices on several other models as an option.
The lights are already available to automobile owners who wish to install them on their own cars. Auto-parts, department and discount stores carry the lights in various colors. They are designed to be mounted inside the car on the rear-window deck.
They sell for about $20 to $25, depending on whether they are equipped with a special circuit that screens out the flashing turn signal. If you don't want to install the light yourself, any garage should do the work for a relatively small charge.
Eventually, auto makers will be designing the additional light into the rear ends of cars, but, for now, most of them will opt to simply mount the light in the rear window or on the trunk.
The highway safety administration believes that the new brake lights will be the most effective accident-prevention standard they have ever put in place. The agency began studying the lights in 1977 and has accumulated about 100 million test miles in highway and city driving conditions. The tests, which were conducted on taxis and telephone-company cars, showed that the lights reduced rear-end collisions by more than 50%.
One unanswered question about the effectiveness of the lights is whether they will prevent as many accidents when all cars are equipped with them. Possibly they are more effective in tests because they are still novel and thus attract greater driver attention.
Still, the lights are certainly far more visible than conventional brake lights, which sometimes are mounted below the normal line of vision when driving.
The third brake light may also be effective in preventing multiple rear-end collisions, because the light should be visible through the windows of cars up ahead. Thus, an alert driver may get advance warning that a car is entering a panic stop much sooner than before.
Q: I recently purchased a 1974 Ford Ranchero with a 351-cubic-inch engine. If it has fully warmed up, it will not start after a short stop. If it cools down for a half hour, it will start. The battery is good. What's wrong?--K.C.
A: Your problem is most likely the result of a bad connection in the large cables that run from the battery to the relay switch and the starter. A bad connection increases the amount of electrical resistance in a circuit and increases the electrical current the circuit draws.
The starter system on an automobile draws up to 250 amperes of power, which is a very large amount of current (more than any household electrical appliance). Any extra electrical resistance will substantially increase the amount of current being drawn and run down the battery.
The problem turns up only when the engine is hot, because heat causes electrical resistance to rise in the cables, the connections and in the relay switch. Check all three areas and replace the cables and relay, if necessary.
Ralph Vartabedian cannot answer mail personally but will respond in this column to automotive questions of general interest. Do not telephone. Write to Your Wheels, You section, The Times, Times Mirror Square, Los Angeles 90053.