President Carter's proposals to conserve energy may be headed for defeat in Congress, in part because of backlash against his decision to lift price controls on domestic crude oil.

Members of the House and Senate committees handling the conservation measures, sent to Congress last month, say that three of Carter's four main proposals are in trouble, despite a new push from the president.

"They had real problems on the merits, and now the people who are likely to support them are irritated by decontrol," said Rep. Toby Moffett (D-Conn.), an spoken opponent of Carter's decontrol plan.

Moffett and others on Capitol Hill agree that Congress is likely to approve mandatory themostat settings but may kill standby gasoline rationing, as well as bans on weekend gasoline sales and decorative lighting.

The mandatory thermostat settings-for commercial buildings, 65 degrees in winter and 80 degrees in summer-would save the most oil, about 350,000 barrels a day.

Energy Department officials yesterday conceded that they faced problems winning approval for the other standby measures, especially weekend service station closings, although a DOE spokesman said, "We still hope to get them all, we're fighting like hell."

There has been no formal vote an the standby conservation plans in the House, but according to Moffett an informal vote in the Commerce subcommittee two weeks ago indicated little support for Carter's proposals.

Earlier this week the Senate Energy Committee agreed to support mandatory thermostat settings but rejected bans on outdoor lighting-a measure DOE estimates would save 4,000 of the 19.5 million barrels the nation consumes daily. The committee also deferred action on coupon rationing and on weekend gasoline sale bans.

"There is little enthusiasm anywhere (on Capitol Hill) for the ban on lighting, even as a symbol," says Frank Potter, a member of the House Commerce subcommittee.

On the Senate Energy Committee, Chairman Henry M. Jackson (D-Wash.) has also expressed reservations about the measures' chances for passage.

Sen. Lloyd Bentsen (D-Tex.) is one of a number in the Senate who have objected to the standby rationing plan, which some argue is biased against rural and agricultural states.

Rep. Albert Gore (D-Tenn.) says, "The prevailing opinion here is that rationing is in a lot of trouble." Gore says, however, that it can be saved if the administration sets aside blocks of rationing coupons for states to allocate.

Weekend service station closings, which DOE has estimated would save 240,000 barrels a day, is a measure almost as controversial as rationing. Under stiff opposition from the tourism industry and rural states, both energy panels in the House and Senate have been reluctant to indicate any move toward approval of such closings.

One House Commerce Committee aide, however, said that the House committee may approve closings April 24 when the measure comes before the committee. The full House wil have an opportunity to vote on the issue.

Another factor, according to Gore, is that "the savings appear to be disputed by DOE's own studies." Gore and others also point out that weekend station closings may not be needed because there is growing support for Carter's alternate proposal that the states set their own conservation goals and select their own plans to meet them.