August in Vienna and the central air is down, and the repair man is kneeling in a closet in a basement, dripping sweat on the floor. The sweat is beading his forehead and dripping down his cheek, hanging on the end of his nose and rolling off his fingertips. His knuckle bleeds and his wrist crackles as he turns a screwdriver, and his shirt is soaked from his neck to his chest, where a little white patch with red lettering tells that his name is Howard.

Howard Davis, 42, air conditioning repair mechanic. Ninety degrees, 82 percent humidity, $45 for the first 45 minutes, $9 for each 15 minutes thereafter, 40 to 100 percent mark-up on parts. But when the air conditioner dies, the housewives of suburbia welcome Howard Davis in his white Chevy van like a knight on a white charger, begging his boon, hoping for a champion against the great green dragon of summer heat.

He answers the calls via two-way radio, dispatched from Muse Service Company in Tysons Corner, and he knows which house without knowing the address: It's always the one with the windows open. On this day he will drive 100 miles in his 8:30 to 4:30 shift, check the freon at a house in McLean with aluminum Doric columns out front, replace a heat pump belt for an inquisitive German housewife in Kings Park West, tighten a screw in a thermostat at a town house near Fairfax Circle where the Hispanic woman seems to be able to say only two phrases in English, "Air broke," and "You fix? You fix?"

An English woman in Vienna will offer a glass of iced tea and two homegrown tomatoes, and they will debate the relative energy savings of leaving the air conditioning on all day or leaving it off and then turning it on when she gets home. Their dialogue is hindered only slightly by their language gap: hers being upper crust London and his being bottomland Tazwell, Va. He says "to-may-toe," she says "to-mah-toe." And not far away, a young accountant, originally from Rising Sun, Md., will feed goldfish to his Oscars while Howard Davis sweats heavily in the basement closet of the rented house.

Davis will sweat and kneel, run back and forth 10 times to his truck, parry suspicion and doubt about his honesty. But Davis keeps smiling, keeps making his best attempt at country pleasantry, for he has been an air conditioning repairman for 12 years, and is acquainted with the elemental truth of his trade: It's always hot where an air conditioning repairman sojurns. And it never cools until after he leaves.

Howard Davis is in his van in the driveway of the house in McLean, and the Timex watch hanging on the shift lever reads 9:05 a.m. The truck is cluttered with $6,000 worth of tools he has accumulated. He buys them himself on his $9-an-hour salary. On the floor are countless wounded screwdrivers. He goes through at least one a month, $4 each at Sears. On the console are a plastic comb, 10 packs of matches, assorted screws and nuts, a couple of Band-Aids and a large 7-Eleven coffee cup filled with quarters. The quarters will be spent next week, when he takes his 25-foot Titan motor home to Atlantic City. "Love those slot machines," he says.

He has finished his job in McLean and the radio crackles: "KRY 518 to 105." The voice is a woman's. Howard's wife, Virginia, is the dispatcher. Davis picks up the microphone.

"105 bye."

"Hey, Howard. Woman in Kings Park West with a gas air conditioner says she couldn't bring air up at all. She had the gas company out twice and they told her the heat anticipator would have to be replaced." Virginia gives the address.

"10-4," Howard answers. "105 out." He shakes his head and scowls.

"No," Howard says in a voice slightly louder than a whisper. "The heat anticipator has nothing to do with the air conditioner. Those gas company guys. You'd think they'd know what they're doing. Not that all of them don't, just that some of them don't know anything more than how to find a gas leak. They get the customers all upset."

And at the house in Kings Park West--the house with the windows and the screen door open--the customer somewhere inside sounds upset. "No, Fluffy, no. Get off the rug. Bad dog," a woman's voice shrills.

"People get edgy when they don't have no air," Davis says, shifting his tool box from his right hand to his left. It is now 9:45.

A platinum blond woman with a German accent appears. Her hair is rolled and she's wearing a terry-cloth tennis outfit. He says "Howdy." She tells the frenzied story.

"It was so hot we couldn't sleep all night. I'd put it down to 60 and it would go on but then it would shut off. The gas man said it was the thermostat, the heat something."

"The heat anticipator, ma'am, but the heat anticipitator has nothing to do with the air conditioner."

"But we have gas air and heat."

"I know, ma'am."

Davis walks over to check the thermostat, hidden behind a hanging plant. He removes the plant from it's ceiling hook but finds that the bottom vines are stapled to the wall.

"Sorry," the woman says, removing the plant. "The thermostat is just so ugly . . . Oh, do you think a fuse could have blown. Gosh, I never checked."

"Might well do that, ma'am."

The phone rings. The daughter, about 5 years old, picks it up. "Hello Daddy . . . . I'm just standing here talking to you on the telephone . . . . Yes, the repairman is here . . . . Okay. Mommyyyyy!"

Davis checks the thermostat with his Amp Probe, a meter with little wires that he touches here and there to see if there is power in the thermostat. Then he goes outside to check the unit. The lady of the house follows. The unit is a Bryant heat pump, No. 3645300, Series D. There are flowers and shrubs planted around the gray metal box in the back yard. "For some reason they always plant this stuff around the units, and I always have to step in the stuff to get to it," Davis says.

He turns off the power to the unit, always the first step. Once he turned off the dishwasher circuit instead of the air conditioner. When you take 220 volts through a wire cutter it leaves the taste of copper in your mouth, Davis says. He takes off the cover, stares at the wiring box. Suddenly, the unit cuts on.

"It's fixed," the housewife squeals.

"Nope," Davis says. "But I know the problem."

He reaches down inside the unit, pulls out a severed rubber belt, 32 1/2 inches long, 5/16 of an inch wide. "It's this little old grooved pump belt, ma'am."

"Then you can fix it?"

"Yes, ma'am, sure can."

"Bless you, sir."