It's curious what can make an impact on a life. For 25-year-old Charles E. Bean of Arlington, it was a couple of raw deals at a used-car lot.

When he was 16, Bean paid $1,500 cash for a 6-year-old car with 70,000 miles. The dealer had assured him it was in good condition.

"I drove it for three days. Then I couldn't get it into reverse. The transmission went out. At that age, I didn't know I had any legal rights." When the dealer refused to make repairs, Bean abandoned the car as a total loss.

At 19, he tried again, paying $2,800 for a 3- or 4-year-old compact with about 38,000 miles on the odometer. At the end of the 30-day warranty, the car--"a lemon"--broke down. "I was so angry," he recalls. He had to borrow money to get it fixed.

Six years after the last incident, and as he was searching for a consumer-oriented business to get into, Bean decided he might spare other used-car buyers his misfortunes. Seven months ago he formed the Car Buyers Advisory Service with this slogan: "Don't pick a lemon."

After reading the repeated recommendation of consumer advisers that used-car customers take along a mechanic, he asked himself, "But where do you get that kind of service?"

He decided to provide it. Like hiring a house-inspector before signing a contract, you can hire a used-car inspector from Bean's firm. He thinks his is the only one of its kind in the area, and perhaps the country.

High interest rates "are forcing more consumers into the uncertainties of the used-car market," he says and cites estimates that three out of four cars bought for personal transportation are used.

Says Jill Tanner of Arlington County's Consumer Affairs Office, which gets many buyer complaints (130 in 1979; 68 in 1980): "They take it home and it falls apart and they can't return it. They take the dealer's word the car is in good shape, and it isn't."

On Aug. 14, 1981, the Federal Trade Commission issued a rule that--if not vetoed this spring by Congress--will require used-car dealers to post a window-sticker detailing a car's warranty coverage and certain mechanical defects known to the dealer.

"The primary purpose of this rule," says the FTC, "is to prevent and discourage oral misrepresentations and deceptive omissions of material facts by used-car dealers. . ." The rule has run into trouble in at least one Capitol committee.

Bean, who had been working in the business office of a New York toy manufacturer, faced one big problem before he could set up shop: He knew little more about a car's mechanical parts than when he made his unfortunate purchases as a teen-ager.

He put an ad in the paper for part-time certified mechanics, eventually signing up three, including Robert Wahl, who teaches a consumer-oriented course on auto mechanics at Prince George's and Anne Arundel community colleges. Bean also took on as a consultant Noel Dawson, who retired two years ago as chief of the District of Columbia's registration and vehicle safety-inspection division. Dawson's first task was to devise a 52-item inspection checklist which includes mechanical and electrical systems, and the possibility of body repairs.

Bean now offers these options:

* With two-hours' notice, a mechanic will accompany a potential buyer to a used-car lot (or private seller) to inspect and road-test the car. Fee: $50. (If the mechanic advises against buying, the cost of subsequent inspections is reduced.)

* With three-hours' notice, a mechanic will pick up a car and take it to one of two service stations for a more thorough inspection. (The stations make no repairs.) Fee: $65.

* With a three-day notice, Bean--who is fast-learning about cars--and his staff will search for, inspect and purchase a used car as close to the buyer's specifications as possible. Fee: $150.

"One lady," says consultant Dawson, "bought a car without ever seeing it." After he had pointed out defects in her first choice, "she was so grateful" she asked him to find one in better condition. "I got the dealer to give her two new tires. She came out good on that deal."

Most people, says Bean, believe they'll get an honest deal from an individual. "But times are changing. They need to scrutinize individual sellers as much as the dealers."

In all cases, he says, the repair, recall and test-history of a particular make and model will be checked and the buyer will be advised on the going price for similar cars in the same condition. He or a staff member will do the bargaining for those who shy away from that kind of confrontation. He claims often to have saved clients $200-$300 over the original asking price.

Constance Adler of McLean and her husband Robert, who is with the Agency for International Development, phoned Bean in January with a make and model in mind. "He told us to stay away from a '78," she says, because of repair problems. When the Adlers spotted a '79 advertised in the paper, Bean dispatched a mechanic.

"The only thing they found wrong was a rattling ashtray," says Adler. "They even dickered the price down $150." The first time the Adlers saw the car is when they showed up at the dealer's to sign the contract. So far, they're "happy" with the purchase.

Although Bean does not guarantee that something won't go wrong with a purchase, "We try to get the dealer to correct any defects before delivery." If they don't, he subtracts the repair cost from the price he suggests that a customer pay.

"We turn down a big percentage of cars," says Dawson. "A whole lot are worn out before they are traded in." But he also sees "a whole lot of good cars" on the market and considers used vehicles "still the best buy."

Most dealers have been cooperative so far, although Bean says some have told customers his inspection service is unnecessary. And one "cussed out" Dawson after he told a client the model she picked had a "terrible repair rating." If a dealer isn't cooperative, Bean advises his clients to shop elsewhere.

Although Bean bought a new car three months ago--he drives more than 200 miles a day--that hasn't meant the end of his automotive woes. He woke up to find the car stolen the other day.

For more information: Car Buyers Advisory Service, 1008 N. Randolph St., Suite 205-E, Arlington, Va. 22201. Phone 276-1966. Hours: Monday through Saturday, 9 a.m.-7 p.m.