QUESTION: Why does a car's passenger-side mirror show objects to be farther away than they are, while the driver's side has a "regular" mirror?
--Margaret Dambley
ANSWER: Good question, Margaret. Your passenger-side mirror is a convex mirror, with an outward curve in the glass surface, which allows a greater field of vision. While seated behind the wheel, your eyes are about two feet from the left side mirror and six feet from the passenger side mirror. The longer distance between eyes and passenger-side mirror would result in a narrow view down the right side of the car were it not for the mirror's assistance.
The downside of a convex mirror is that objects appear smaller, or farther away than they actually are. To best utilize a side mirror's field of vision, it's a good idea to adjust the mirror so the side of the vehicle is barely showing at the inner edge of the viewed image. This allows the widest possible viewing of angular threats. On vehicles having sufficiently large mirrors, a small, stick-on convex auxiliary mirror is a nice addition to the driver's side mirror.
Q: My battery is six years old. I know this is pretty old. Is there a way to test it (at home) to know if it's still dependable?
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--Jerry Lieman
A: You're correct that this is a mature battery. How did the engine start this past winter? If all seemed well on the coldest mornings, this is encouraging. A professional might test your battery in one of two ways -- either a traditional load test, or a more techie check of the battery's cell conductance.
Let's create a home version of the load test.
Using a simple voltmeter -- the Sears Craftsman Digital Mini Multimeter, model #82345, is a superb value at $22 -- check the battery's open-circuit voltage, meaning nothing is turned on. A fully charged battery in good condition should read 12.6 volts or higher.
Next, if possible, determine a method of disabling the vehicle's fuel system, such as by removing the fuel pump fuse or unplugging fuel injectors. Now crank the engine for fifteen seconds with meter leads clipped on to the battery terminals, observing battery voltage on the meter. If the voltage remains steady and above 11 volts, it's still in competent condition. Should the voltage fall below 10 volts or noticeably decline while cranking the starter, I'd start shopping for a battery now. If the readings fall somewhere between these two values, I'd consider renewing the battery in October or November, before the onset of cold weather.
A less invasive but less conclusive test method is to observe the battery's open-circuit voltage, then turn on the headlights, with the car's key turned to "off," for fifteen minutes. If the battery voltage dips below 12.3 volts or if the engine is noticeably slow to crank afterward, the battery is in marginal to poor condition. To play it safe, before employing either of these methods, be sure you have the means to jump-start or recharge the battery, should the battery be in poor condition.
The easiest option may be to ask for a free battery test at an auto parts store. Ask for an interpretation of condition rather than a simple pass/fail pronouncement. On the three differing conductance testers I use in class, each will "fail" a battery that's still 49 percent capable. With mild weather and a pair of jumper cables onboard, one could stretch such a battery for at least another two or three years.
