Two Washington automotive repair shops have filed a class action antitrust suit in federal court here against the Mercedes Benz Corp., charging the German car manufacturer with "artificially" inflating the prices of parts for the car.

If the suit is successful, damages "would have to run into the millions of dollars," one of the attorneys for the independent garages said today. He declined to be named, however.

Technical Learning Collective, Inc., of 1219 13th St. N.W. and Lad Mills, Inc., of 1545 Wisconsin Ave. N.W. filed the suit in U.S. District Court late Friday against Daimler-Benz Aktiengesellschaft, the West German manufacturer of the car, and Mercedes-Benz, Inc., of North America, the Chevy Chase office which is the "exclusive distributor of Mercedes Benz automobiles and parts in the United States," according to the complaint.

"Mercedes imports the parts from Germany and, pursuant to an agree- ment with its own dealers, sells the parts to independent garages through its own dealers," said the attorney for the auto repair shops. "The dealers increase the price of the parts to the garages by 20 to 30 per cent.

"The independent garage, then, is probably forced to overcharge its customers, and he can't compete with the Mercedes dealers.

The suit charges the Mercedes distributors with excluding at least 10,000 independent garages that repair imported cars from the lucrative 6Mercedes market since the alleged "conspiracy" begn in 1965.

In 1976 alone, Mercedes sold "in excess of $50 million" worth of automotive parts, according to the complaint.

Uwe Wazenegger, general manager of Mercedes for the Washington zone, said today he "had not been served with any suit papers" and wasn't aware the suit had been filed.

But he denied that Mercedes monopolized the parts market or fixed the prices for Mercedes parts.

In 1974, Mercedes was sued by a Pennsylvania consumer group for allegedly conspiring to fix prices for auto repairs and labor charges. Mercedes lost the suit but appealed its class action nature to the U.S. Supreme Court, which refused to hear the appeal.

The independent garages are asking the federal court to free the Mercedes repair market for competition by permanently enjoining any "combination, conspiracy, agreement, understanding or concert of action" to hold their monopoly on the parts market.

They also seek a judgment of triple damages.