The House, seeking to blunt the impact of early television projections of presidential election outcomes, yesterday approved legislation that would set a uniform closing time for voting in presidential elections in the 48 contiguous states.

The measure, adopted 204 to 171, now goes to the Senate, where its fate is uncertain.

Under the legislation, voting in the presidential general election would end at 9 p.m. in the Eastern Time Zone, 8 p.m. in the Central Time Zone and 7 p.m. in the Mountain Time Zone. In the Pacific Time Zone, the bill provides for up to a two-week extension of daylight savings time during presidential election years, allowing West Coast polls to remain open until 7 p.m. daylight time, the same as 9 p.m. standard time in the East.

Alaska and Hawaii would be exempt from the uniform poll-closing time, but 39 other states would have to adjust their voting hours. The measure would extend voting by one hour in the District of Columbia and Maryland, where polls now close at 8 p.m., and by two hours in Virginia, where the polls close at 7 p.m.

The bill was pushed on the floor by two West Coast lawmakers, Reps. Al Swift (D-Wash.) and William M. Thomas (R-Calif.), the chairman and ranking minority member of the House subcommittee on elections.

The poll-closing issue was highlighted by the 1980 election, when President Jimmy Carter conceded defeat to Ronald Reagan before voting had ended in several western states. This was thought to have discouraged some voters from going to the polls and to have affected the outcome of some West Coast congressional races.

Last year, executives of the three main television networks pledged not make projections based on voter exit polls for any state until voting had ended in that state. But Swift and Thomas argued that this pledge would not solve the problem because of time zone differences and varying poll-closing times.

"The problem is an antiquated election system across the U.S. that does not provide for a uniform closing time," Thomas said.

The bill was strongly opposed by Rep. Bill Frenzel (R-Minn.), who unsuccessfully offered crippling amendments, including one to include Alaska and Hawaii under its provisions. Frenzel, calling the bill unneeded and disruptive, said, "We are doing social tinkering with the most precious franchise of the American people to satisfy a few people on the West Coast."