Michael Bernhard says he was driving about 30 miles an hour on a Florida highway in March when he applied his brakes.

The car swerved violently to the left and crossed into the oncoming traffic lane before Bernhard could control it. He didn't hit anything, but the close call left the Charlottesville motorist scared and outraged, igniting a letter-writing campaign to federal safety officials, consumer groups and Chrysler Corp., the manufacturer of his 1978 LeBaron.

The same accident happened to Clifford Lohs of Elgin, Ill., in September 1977 and Helen B. Ward of Palms, Calif., the month before. His car was a Dodge Aspen, hers a Plymouth Volare.

Steve Wodka's car went out of control on a turnpike exit ramp near Philadelphia two years ago. The right front brake locked without warning, he says, pulling his car sharply in that direction. Wodka's Aspen was going 50 miles an hour at the time. "It took all my might to keep it from going off the road," he said later.

When Wodka tried to have the front brake repaired, he found there were no replacement parts available anywhere in the Philadelphia area, and the car had to be towed to Washington, where he works as a labor union official.

Chrysler repairmen told him the problem was "happening all the time," the same story Bernhard got from three brake shops in Ft. Lauderdale.

By the spring of 1978, the National Highway Traffic Safety Administration had received enough complaints like these to begin an investigation of front disc brake problems with Chrysler Corp. on cars beginning with the 1976 model year.

Today the agency's files show hundreds of complaints, some of them volunteered, many made in response to NHTSA queiries. Their complaints make a harrowing tale of break-downs, costly repairs, close calls and some serious accidents.

The federal agency has not decided whether the brake problem is a "safety defect" that requires a recall -- a judgment that could saddle Chrysler with a huge bill for repairs on more than 2 million cars, or whether it is merely a "repair" dispute that car owners and the company will have to fight out.

However that question is answered, the disc brake problem has already wounded Chrysler. Since 1976,, when the disc brakes were first installed on the new Dodge Aspens and Plymouth Volares and other company models, Chrysler's hardearned reputation for engineering skill has been battered in the eyes of many American car buyers.

Chrysler's competitors have had product safety problems equally as serious, or more so, in the past decade. But for Chrysler, the problem could hardly have come at a worse time.

The Chrysler disc brakes included an innovative part -- a plastic piston that provides braking action by squeezing brake pads against a disc on the wheel axle. Such pistons are usually made of steel, but Chrysler switched to plastic, which would not rust or corrode.

Bernhard, Wodka and other Chrysler product owners were told by repairmen that the plastic pistons were to blame for the locked brakes.

Other repairmen, like Dan Hoffenbecker of Washtenaw, Mich., blame a rubber dust boot, a type of gasket that fits between the piston and the surrounding metal brake caliper to prevent corrosion and permit the piston to slide smoothly in and out as the brakes are applied.

In most cases Hoffenbecker has seen, the dust boot had slipped out of place, exposing the surface of the caliper to rust and corrosion. Although the plastic piston surface could not rust, it is softer and more easily scarred than a steel surface would be, he says. As corrosion increased, the chances of the brake locking also increased.

Hoffenbecker, who had a long interview with Chrysler engineers, believes the brakes fail because the dust boots are "put in wrong" on the assembly line. Proper installation is a difficult, painstaking task -- the lip of the boot must be firmly fixed in a groove in the caliper -- and an assembly worker under pressure may not do it right, he said. The mistake would be hard for a plant inspector to spot because of the dust boot's location, he added.

It is impossible to predict when an improperly installed dust boot would work loose, he added.

Chrysler's view of the problem is contained in a series of letters to Lynn Bradford, director of NHTSAs defects investigation unit.

The company said last August it would redesign the piston, moving the groove that holds the dust boot to decrease the chance of slippage.

By February, the only pistons going into new cars or being shipped as replacement parts were the new ones, the company says.

Chrysler also has promised NHTSA that it will redesign the dust boot and caliper, adding a steel ring to anchor the boot firmly in place. The change is an expensive one, Chrysler told NHTSA, but it will be completed for the 1981 model year cars coming out this fall.

In reviewing these changes, William R. Kittle, Chrysler's director of vehicle safety, stressed the brake issue was a "customer dissatisfaction" problem rather than a safety issue.

Chrysler says that long before an accident could occur, motorists would notice a "pull" in the brakes. " . . . the prudent driver will react to the obvious symptoms and will have the indicated maintenance performed," the company says. Wodka and several other car owners insist in interviews that their brakes locked without warning.

NHTSA's opinion isn't revealed in its public correspondence with Chrysler. Bradford wrote to Bernhard saying the problem is under study, but in the meantime, "we have no authority to become involved in disputes between owners and dealers or manufactures regarding non-recall automobile repair work."

A substantial number of Chrysler disc brakes have, in fact, been repaired. A year ago, Chrysler reported that 13,890 brake pistons had been replaced at company expense under its one-year warranty. About half that many brake calipers had been replaced. The total number of brake repairs was 20,854.

However, NHTSA's files suggest that many Chrysler drivers did not notice the problem until after a year, when they -- not the company -- would have to pay for repairs.

A more complete measure of the problem is the sales of replacement brakes. According to Chrysler, 135,529 replacement parts had been sold between 1975 and March 1979.

The sales of new pistons outnumbered sales of calipers and boots by 10 to 1, indicating that in most cases, the entire brake had failed before the repairs were performed.

For Chrysler, the dilemma is harshly ironic. Fighting to regain the confidence of car buyers, it needs all the good will it can muster from former owners. But with no money to spare, it can't welcome a flood of brake repairs at company expense.

Bernhard sent his bill to Chrysler, demanding they pay it. The company replied:

"Naturally, we were sorry to learn of your dissatisfaction . . . However, we are sure you will appreciate that we are not in the position to have an indefinite warranty . . . because your vehicle is beyond that warranty limitations, we are unable to accommodate your request. If in the future we may assist you in some other area, please be sure to write."