Unless you're a car mechanic yourself, dealing with a repair shop may require a leap of faith. But if you pay attention to what your mechanic says (and does), you'll find clues to tell you whether you're being bamboozled.

Here are some things mechanics may say when they're planning to take you for a ride:

• "Get that engine flushed right away or it's toast." Beware if your mechanic's idea of "scheduled maintenance" bears little resemblance to the recommendations in your owner's manual. Some shops "build the ticket" (translation: pad the bill) by recommending extra and often unnecessary procedures, or by scheduling some tasks prematurely. Some hawk high-priced "generic" maintenance schedules that may omit procedures your car needs. Be especially concerned if the shop makes every recommendation sound like an emergency.

• "That rebuilt alternator will run you $899." Although good shops may charge higher prices to cover the cost of top-flight technicians and equipment, bills that are always 20 percent to 30 percent more than the going rate should put you on guard, warns AAA, formerly the American Automobile Association. You can poll other shops to find out how much mechanics in your area are charging. For complex problems, try comparing the price of the parts alone by calling parts stores or dealer parts departments.

• "With some cars, it's not unusual to go through a starter every year." This may be a tip-off that the shop did the work incorrectly or used poor-quality or makeshift parts instead of proper ones. Call some other shops to find out what they think, or check the Web to see if there's a discussion group devoted to your model and its problems. You might also want to take the car to another repair shop for a second opinion. If the original job was lacking, ask the shop that did the work to repeat the repair either without charge or at a substantial discount.

• "You'll have to bring your car back to the dealership for service." Generally, you need to use a dealer only for work covered under the warranty, recalls, post-warranty fixes you're hoping the manufacturer will pay for under its "goodwill" program or high-tech systems that require a dealership's specialists.

You can avoid many of these complications — and get the right repairs at a fair price — by communicating clearly with your mechanic at the outset:

• Describe the problem fully. Provide as much information as possible. Write down the symptoms and when they occur. If possible, talk directly to the mechanic.

• Don't offer a diagnosis. Avoid saying what you think is wrong. You may be on the hook for any repairs the shop makes at your suggestion, even if they don't solve the problem.

• Request a test-drive. If the problem occurs only when the car is moving, ask the mechanic to accompany you on a test-drive.

Ask for evidence. If you're not comfortable with the diagnosis, ask the shop to show you. Don't let the mechanic refuse your request by saying his insurance company doesn't allow customers in the work area.

Copyright 2006, Consumers Union