Computers help pinpoint problems under the hood

The engine compartment of many new cars these days looks as if it had been designed by a trash compactor. It's often enough to discourage even the best shade-tree mechanic.

Automobiles have increased in complexity as they've been reduced in size. This makes it much harder to track down problems by standard trouble-shooting methods. Many times the mechanic just can't get to the right spot to check something out.

So mechanics are turning to new computerized testing devices to help them convince you that your car needs work. But do these machines really know what they're doing?

Mostly, they do, but alertness on the car owner's part can better ensure that what needs to be done is done.

Almost always the use of a diagnostic computer on a car is simply a matter of doing the same tests a mechanic used to perform, but in a more efficient way.

In the final analysis, the use of a computer should mean a less-expensive bill to fix the problem. It should also help clarify your own understanding (and the mechanic's) about the work to be done.

If you haven't seen the new computer analyzers yet, you probably will quite soon. In fact, the manufacturers of the new electronic testers claim that few auto shops will be able to function without them.

Typically, an automobile owner will bring in his car for service only when it begins to run rough, misfire, accelerate poorly, or have start-up problems in the morning. In this case, computerized test equipment can be just the thing to find the trouble.

Computerized test equipment is made by such companies as Allen Electronics, Auto Sense, Bear, FMC, Coats Diagnostic division of Hennessy, and Sun Electric. Each kind has different features and capabilities, but all are used to cross-compare your car's various functioning systems against a standard for that particular make and model.

During the procedure the instrument measures several systems: ignition, starting, charging, fuel, emission control, engine operation, and the air-conditioning system. The mechanic will then compare the readings with the values listed in the manual of your car.

Sophisticated testers, such as the Coats 460, have the capability of comparing the measured data with factory standards by using a floppy-disk memory similar to the type used on business and home computers. The specifications from hundreds of car and truck models, both domestic and foreign, are stored on the disks. As new models roll off the assembly line, new disks are supplied to keep the system current.

After a lengthy menu of tests, a paper-tape printout is provided which has high and low results flagged with an asterisk next to any problem area. And that is where even the most sophisticated computerized auto analyzer stops. The state-of-the-art tests are able to call attention to the area or general location of the problem, but lack the mechanic-intuitive ability to solve problems or pinpoint the trouble.

Both older cars and newer ones with microchips installed in the engine can be tested on the machines. But with the newer cars, the tester can ask for further information from the car's computer and the diagnostic codes. Even so, the mechanic still has the job of searching through the service manuals on many of the tricky problems that beset the modern car.

The new diagnostic computers are a tremendous help to the auto mechanic. In many ways, however, the mechanic must be even more knowledgeable than before. Now he not only has to know his cars and the extent of his own capabilities, but also the idiosyncrasies and limitations of his computerized partner.

What can a car owner do to avoid the ''computer said'' syndrome? Don't let the mechanic lose sight of the problem. Try to be succinct in expressing the reason you brought the car into the shop and do not second-guess the cause by going in for a tuneup without specifying the primary reason that you're there, such as slow acceleration, poor cold starts, and the like.

Tell the mechanic how long it was since your car's last tuneup. Then step back and let him and the machines do the job. But don't drive away until you're sure the problem has been fixed.

How good are the computerized diagnostic auto testers? Will they ever replace a good mechanic? Have your car checked out by one and the answer will be as plain as the flashing cursor on the computer's video screen.

The new computerized genies are a tremendously useful tool, but it's unlikely they will ever entirely replace the trained mechanic.

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