BAD CAR-MA

Are today's automobiles more prone to electrical/electronic system failure?

--by Richard Mandel

Consider: in model years '57 through '59, Ford Motor Company produced the Skyliner, a 4000+ pound, 17.5 foot long two-door sedan with a retractable metal hardtop. It wasn't the first auto to do this, but it was the first out of a mainstream manufacturer's stable to show noteworthy production numbers. To make the whole thing work -- that is, open the trunk and cycle the roof while folding or unfolding the front 18 inches of top (so the thing would fit in the trunk) -- took seven motors, ten relays, thirteen switches and nine circuit breakers. Plus, a connection to the transmission linkage to ensure that the top would only be raised or lowered when the car was in neutral. If any of those many components failed, the driver could be rendered non top-us mentus, or worse, left with a half-raised roof that became an air brake, very effectively preventing two tons of car from making highway speed.

But the car still ran, regardless of the driver's comfort.

Flash forward forty years. The cars we drive today have at least one microcomputer to oversee operations of the entire powertrain from the moment the driver turns the key in the ignition. A chip in the security system, and another in the sound system. Higher-end luxury cars may have sensors to maintain interior temperatures by zone, memory devices that return the controls to a particular driver's settings when they start the car, and built-in cell phones that are essentially computerized radio transceivers. Electrical engineers are working harder to prevent all these sophisticated systems from failing, making the car utterly unusable.

The carbeque

On August 24, 1997, the New York Times ran an article by Matthew Wald that warned the readers to be cautious when jump-starting their car. This wasn't an article describing how to attach jumper cables, or don't-jump-start-if-the-battery-is-frozen -- the topic was about what cars require special treatment when jumping, and what cars shouldn't be jumped at all.

According to guidelines prepared by the Automobile Association of America and distributed by the Towing and Recovery Association, jump-starting a Ford requires turning on the heater blower and, if the car has automatic climate control, setting the controls to "defrost." On Subarus, tow truck operators are advised, if using a quick charge battery charger, not to open or close the doors while the charger is attached, as this will damage the Passive Belt Control Unit of the restraining system. Certain models of Nissan require the removal of the power window fusible link prior to jump starts. Saabs should have the radio turned off. And even if precautions are followed with regard to battery voltages from jumper to jumpee, the minute magnetic field produced in the jumper cables can affect sensitive electronics. For example, that magnetic field can make the fuel injectors in Chevrolet Cavaliers dump fuel.

Obviously, the whole idea is to ameliorate a condition where a system can be fried by the once-simple act of helping someone with a dead battery. In fact, many manufacturers are recommending not to even attempt to jump-start the car, but instead tow it to a facility where the battery can be removed and either be recharged or outright replaced. While this is welcome advice to tow-truck operators who would rather avoid sitting in rain or snow, leafing through a manual, it's not much consolation to consumers whose co-worker inadvertently did $600 in damage, with the booster cables he's always used in the past.

Where solutions lie

Many automotive electronic manufacturers have been working on protecting electrical and electronic systems for years. Larry Hach, of Delco Electronics Corporation, Kokomo, IN, says that it is these types of problems that he has designed against for the 19 years he's been with the company. He is now a Staff Engineering Supervisor with Delco, which has produced electronic and electrical components primarily for GM vehicles for several decades, as well as components for other companies. According to Hach, the regulators in Delco engine control modules are designed to handle 26.5 VDC for up to five minutes, a situation equal to two standard batteries at full charge, and a bit extra. Electronic "blocks" prevent damage should jumper cables be installed reversed, and clamping devices in the alternator control load dumps created by sudden induction spikes, as may occur when a battery cable suddenly breaks in an accident.

Some suggest that the problems arise when no protections, or protections rated below what are needed, are installed in subsystems, a move usually precipitated by management fiat, under the guise of product cost reduction to "stay competitive."

Dr. Christopher A. Jacobs, an electrical engineer, points out that it takes appropriately sized diodes to protect DC equipment from reverse voltages, and zener diodes for handling overvoltages. Dr. Jacobs founded Jacobs Electrical Products in 1972 to produce aftermarket ignition modules, basing his design, which adjusts spark output according to engine need, on a variable rate cardiac pacemaker he had developed years earlier. The business grew to include other modules and components sold in the $3 billion special equipment market, and is today the third largest independent ignition manufacturer. The products made by Jacobs Electrical Products, says Dr. Jacobs, may cost the customers a bit more, but the modules last much longer, as do the vehicles into which they're installed. He also points out that ". . .spikes of up to 150 volts occur from problems like a loose battery cable. These inductive spikes chip away at the silicon in system components, eventually causing a component failure. That failure may not occur for 15,000 miles after the battery cable became loose enough to cause the spikes, so the owner usually ends up looking to put the blame on something they did yesterday."

Another hot problem

As any electrical engineer can attest, extreme temperatures are also a swift killer of electronic components. Many system modules are installed under the hood, where they are subjected to heat radiating from the engine. The problem is, engines are running hotter than they did fifteen years ago in an effort to burn fuel more completely to comply with pollution standards.

Typical measures to protect systems are found in Delco's products, according to Hach. To cope with a standard of 125°C underhood temperature, the IC's used are designed for a tolerance of up to 150°C. Modules are also equipped with thermal protection and thermal shutdown circuits.

Thermistors used for thermal protection in Jacobs ignition products perform extra duty--they aid in adjusting the spark. Since the energy required to fire a cylinder's air-fuel mixture is less when the engine is hot, the thermistors act to inform the module to modify the output, extending the life of ignition components. The modules also benefit from a unique heat protection device. The internal components are coated after assembly with a wax-like material that melts at a specific temperature, drawing heat away from the components as it changes phase. That thermal energy is drawn away by the encapsulation material used to pot the module, and finally through the module's casing that is also designed for maximum heat radiation.

Placement of modules under the hood plays a very large part in extending the life of electronic components. Engineers for years have taken advantage of airstreams along fender walls, even tapping into the ducting to the air cleaner. FEA software today permits designers to test thermal energies in underhood designs directly on their workstations.

The cars presently on the drawing boards will be even more dependent on sophisticated electronic systems, as proposals for navigation systems and more exotic engine controls are made. All-electric cars will also require unique buffers against electrical assault and heat transients, as they gradually replace internal combustion vehicles. Electrical designers, it would seem, have their work cut out for them.

For more information, contact:

Delco Electronics Company, One Corporate Center, Kokomo, IN 46902-9005. 317-451-0908.

Jacobs Electronics, Inc., 500 N. Baird Street, Midland, TX 79701. 800-627-8800.

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