Metro officials have ordered that the five new elongated buses serving Chevy Chase must have functioning air conditioners at all times, even though the air conditioners on some of the new buses serving Benning Road's working-class neighborhoods in Northeast are broken, according to a memorandum posted in a bus dispatcher office. "These five blocks (buses) must have air conditioning as per Mr. Trimmer's orders," says the memo, handwritten in red felt tip pen and dated July 24, 1979.

Trimmer is Thomas Trimmer, director of Metro's bus services. The five buses in question are among 43 new, $173,000 buses that look like according on wheels and that began service July 18. Most of the buses have been running along Benning Road Northeast, while five operate along Connecticut Avenue, from Chevy Chase to the Federal Triangle, in the morning rush hour.

Breakdowns, as well as other mechanical failures, have occurred in the air-conditioning systems of at least half the new buses, according to officials.

"It's like being in a giant sauna bath with your clothes on," said M.E. Fleming, 34, a Metro driver who pilots the new buses along Benning Road.

"There's no circulation, so people pull open the emergency windows and prop them open with their hands, cans, umbrellas, whatever they can get hold of."

Sources said yesterday that the order to route onlgy air-conditioned buses along Connecticut Avenue came by telephone from Trimmer.

Trimmer denied that he issued such an order to dispatcher at the Bladensburg terminal in Northeast Washington, but he said that he "might have discussed" such a plan.

"I have many discussed" such a plan.

"I have many discussions throughout the day, and I could very well have discussed it," he said. "But I've put no memo out to this effect and don't intend to put one out."

Later, Trimmer ordered the memo taken down.

Richard S. Page, Metro's general manager, said he doubted such a "selective" order would have been issued since it would be against Metro policy to show favoritism for one route over another.

"We'er concerned about all 43 buses, whether they run on Benning or Connecticut or anywhere else," he said.

He said that if such an order existed it was spurred by Connecticut Avenue passengers who complained last week that they, too, were hot.

"Black people are on Benning Road and white people are on Connecticut Avenue. It's favoritism," said Walter Tucker, a Metro driver running for the presidency of the Amalgamated Transit Union's Local 689.

"There should be no specification what bus goes where," he said. "It should be the luck of the draw. That's the way it normally is," he said.

Trimmer said the new, 85-passenger buses were assigned based on the "maximum productivity" they would yeild for each route and that the buses were picked for Benning Road and Connecticut Avenue based on the two streets' rush-hour loads.

"No preference is given to any route," he said. "Out entire fleet is equipped with air conditioning."

Trimmer said that the five buses dispatched to Connecticut Avenue serve Benning Road passengers before and after their Chevy Chase runs.

"So if you're providing air-conditioned buses on Connecticut Avenue, you're also providing them on Benning Road," he said.

He said such complaints are the nature of the bus business. "The Connecticut Avenue people say the patrons on 14th Streets and 16th Streets get better service. It's been going on for years." CAPTION: Picture, Metro has had considerable trouble with the air conditioning systems on it new bus model shown above. By Fred Sweets, The Washington Post