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Electronic stability helps keep drivers safe

| Saturday, May 11, 2013, 12:01 a.m.

Q: I want to learn about stability control. How does it work? How do I know what it is doing? Will it improve the way I can take corners? — Paula H.

A: Electronic stability control, or ESC, has been available under many names for close to twenty years. Typically managed by the antilock brake control unit, in conjunction with other vehicle controllers and components, ESC helps bring a vehicle in line with what the driver intended. ESC is not intended to be a performance enhancement; it's there to help get you out of trouble as the vehicle becomes loose. Because of its proven benefits, ESC is federally mandated on passenger vehicles.

Several sensors are used, such as vehicle speed, yaw, steering angle and lateral acceleration. They determine the speed of each wheel; the degree of vehicle rotation, or turning; the driver's steering motions; and actual direction, which includes veering or sliding. Should the vehicle fail to turn in harmony with the driver's intentions, engine throttle is adjusted and individual wheel brakes are applied to straighten things out.

You won't hear or see ESC activity until the car is pushed to a predetermined level of instability. An illuminated instrument panel lamp and/or tone will indicate ESC is intervening and the assistance may come in so smoothly, it may be difficult to determine how it is being done. I've noticed vehicles built perhaps 5-10 years ago intervened somewhat early and clumsily, seemingly scolding you with a large and lingering throttle reduction, while newer ones are smarter and take action more seamlessly.

Q: I recently endured a problem with my car where the battery went dead while driving. It was the alternator that needed replacing. I was told if I had noticed the voltmeter reading incorrectly, I might have been spared the breakdown. How might this have looked on the meter? — Raymond Peralta

A: While under way, a vehicle's charging system tries to maintain a system voltage of around 14-14.8 volts. When you see this on the instrument panel gauge, it's safe to assume electricity is being generated at a greater rate than is being consumed, and not in excess. At idle, with many accessory loads active, voltage may temporarily dip to perhaps 13-13.5 volts, as the charging system isn't as effective at low engine speed — but this is OK. A gauge reading below 13 or above 15 indicates a charging system fault. A low reading may lead to a discharged battery; a high reading may cook the battery and certain vehicle components.

Brad Bergholdt is an automotive technology instructor at Evergreen Valley College in San Jose, Calif. Readers may send him email at under-the-hood@earthlink.net; he cannot make personal replies.

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