The District's dilapidated network of traffic signals got a harsh taste yesterday of one of winter's most exasperating misfortunes: a broken oil furnace.

Most of the city's 1,275 traffic signals were thrown out of whack during the morning rush hour after the heater went kaput in an obscure District building that houses some crucial apparatus. Many red signals took longer than usual to turn green. Some stayed red for several minutes. Traffic stalled.

"In a sense, our traffic signals had to shave with cold water this morning," George W. Schoene, city traffic services chief, said after the malfunction had been fixed. "What happens is everything slows down."

"The whole town was screwed up," said Robert Nicholson, a city traffic police officer. Drivers were "growing impatient. There were scores of people running red lights."

The signal slowdown was blamed on the breakdown of a large oil furnace in a two-story building at 1338 G St. SE, the site of the city's signal shop. The office contains gadgets that send radio signals to the traffic lights. These signals tell the lights when to start each cycle.

When the furnace went on the blink sometime during the night, the temperature inside the building plummeted. Lubricants apparently got thicker and gears turned more slowly inside the traffic signal equipment. Radio signals went out less frequently than they should.

So many traffic lights stayed red too long. They could not change to green, officials said, until they received a radio signal to start another cycle. Normally, these signals go out every 40 to 120 seconds, but yesterday many of them were markedly delayed. "You sort of stop your watch," said Schoene.

When signal workers arrived at the shop yesterday morning, they resorted to electric heaters to warm the balky machinery. The furnace breakdown later was attributed to an apparent vapor lock, an air bubble in the fuel supply system. By 11 a.m., the traffic lights were back to normal, officials said.

But even under normal circumstances, officials said, the District's traffic signals are prone to mishaps, especially in winter. Metal components in the mechanisms attached to each traffic light tend to shrink in the cold. Gaps in electric switches fail to close. Lubricants thicken.

"Weather affects them. Cold, snow, extreme heat affects them. The parts are over 30 years old," said a D.C. Department of Public Works spokesman. In cold weather, many traffic signals are apt to change too slowly, officials said, and some are likely to stop working.

Nonetheless, city officials have promised relief. Over the next five years, the District plans to carry out a federally financed $34 million program to replace the outmoded, mechanically run traffic signals with electronic devices. The first 500 modern signals are to be installed in the downtown area later this year and next.

As a precaution against mishaps such as the one yesterday, the new signals will be outfitted with two backup systems. The new system will be foolproof even against a discombobulated furnace, Schoene said.