In July of '78, I wrote about the frequency with which the District government's air conditioners break down.

A reader had informed me that the heat in the headquarters of the police department's Fifth District had made him ill. "I don't see how the policemen who work there can stand it," he said.

When I looked into his report, I found that the cooling system at 5-D had been inoperative since the summer before. Lack of routine maintenance was blamed. "It should have been checked a month before the onset of warm weather," I was told. But it wasn't, and when there was need for cooling, the system was as dead as a doornail.

What's more, I was told that the cooling systems in other government buildings were also defective. A mysterious phantom appeared to have cast an evil spell on them.

The building that houses 5-D is of modern design. Its windows do not open. The rationale is energy conservation - a laudable aim.

But when cooling systems in such buildings malfunction, temperature inside can rise to more than 100 degrees. How would you like to work in an environment of that kind during Washington's prolonged heat waves?

When I wrote about the problems at 5-D last July, two major concerns were in my mind: the long delay in making repairs, and the possibility that the District's budget-makers were skimping on maintenance. That's an old political trick: Trim the budget where it won't show right away, and let the next administration worry about expensive replacement costs.

Last year's column about cooling system breakdowns was recalled to my mind when I learned during last week's heat wave that Fourth District headquarters had been without air conditioning for some time. A reader who went there to make a report said he saw a thermometer that registered 110 degrees. And of course 4-D is also in a relatively new building in which the windows can't be opened.

I phoned 4-D's top man, Deputy Police Chief Charles M. Troublefield, and asked him what was wrong. He told me that trouble in an electrical line had caused the cooling system motor to burn out, and that repairs were under way. When I asked whether the unit had been given proper maintenance, Troublefield said he wasn't really qualified to pass judgment on that. The Department of General Services handles maintenance for the police department.

My next call went to Roy Korth, a management analyst in the police property division. "Here we go again, Roy," I said. "This year it's 4-D instead of 5-D. What's the story?"

"This time it was a freak accident, not a lack of maintenance," he said. "The motor was completely burned out, and it's a huge thing: 150-horse-power. It takes time to get a replacement for that size."

"How much money are we talking about?" I asked.

"About $30,000 for the whole job," he said. "Talk to Ron Mordecai, the assistant director of DGS for Building Management."

So I called the Department of General Services. Mordecai assured me that preventive maintenance is provided routinely. He said the trouble at 4-D had occurred when an electric line feeding the cooling unit had "lost a power phase during a storm."

I put the key question to him bluntly: "Is there enough money in your budget for preventive maintenance?" His answer was that a reasonable amount of maintenance money is budgeted. Sure, every government agency can always use more money, but DGS makes out fairly well with what it is given. In this case, nature had cause the damage, not lack of maintenance.

Just for luck, I got one more opinion. Harold Henson, assistant DGS director for Repairs and Improvements, told me the motor had indeed appeared to have been damaged during a storm. He said he had seen no evidence of a lack of maintenance.

The good word for those who must work inside 4-D headquarters is that if all goes well, repairs will be finished by Monday or Tuesday (the 18th or 19th). Meanwhile, our policemen can do little more than pray that the Great Police Chief in the Sky will continue to keep Washington's temperatures at a reasonable level.

In researching stories of this kind, I get the strong impression that our architects and temperature-control specialists still have much to learn. There are public and private buildings all over town in which some areas are too warm while others are too cool - even when the system is working at its best. When the system malfunctions, the people who must live with it begin to wonder how long it would take to invent a window that opens.