The Senate Foreign Relations Committee voted last night to prohibit the use of any U.S. foreign aid money to help the "contra" rebels fighting the leftist Sandinista government in Nicaragua.

The 9-to-6 vote by the committee came after it had defeated on largely party-line votes a series of proposals by Sen. Christopher J. Dodd (D-Conn.) to put limits on President Reagan's controversial policies toward Central America. Dodd was defeated again, 10 to 8, when he proposed barring use of aid money for the contras directly or channeled through third-party countries.

Sen. Claiborne Pell (D-R.I.) then seized on the first part of the Dodd amendment and won the committee's backing for language stating that no money in the $12.8 billion aid bill for fiscal 1986 can be spent to assist the contras. Committee members noted that this applies only to foreign aid funds and would have no effect on an expected vote by Congress later on whether to resume covert funding of the contras through the Central Intelligence Agency.

In an action separate from the foreign aid bill, the committee unanimously approved a proposal on South Africa by Sen. Charles McC. Mathias Jr. (R-Md.). It would provide a two-year grace period after which the absence of improvements in South Africa's treatment of racial minorities would require Reagan to report to Congress on his progress toward a program of economic sanctions.

Committee Chairman Richard G. Lugar (R-Ind.) said the South Africa issue was too important and complex to be treated as part of the foreign aid bill and should be considered in detailed separate hearings. At his request, Mathias then agreed to separate the South Africa proposal from the aid bill.

The committee also defeated, 9 to 8, a bid by Sen. Alan Cranston (D-Calif.) to prohibit U.S. government loans to South Africa.

Earlier last night, ignoring administration objections to "artificial mechanical formulas," the panel voted to keep the ratio of U.S. aid to Turkey and Greece. It decrees that, for every $10 given Turkey, Greece must receive $7.

The panel also voted to ease the administration ban on U.S. aid to private organizations and international agencies that support abortion as an aid to population control.

But, in a seemingly contradictory move, it barred use of such funds by those organizations with programs in China or "any country which permits . . . infanticide or coerced abortion."

The committee later passed the $12.8 billion foreign-aid bill for fiscal 1986, 15 to 1, with Sen. Jesse Helms (R-N.C.) voting no.

The committee, accepting arguments that a gesture on aid might improve strained U.S.-Greek relations, kept the 7-to-10 ratio by cutting the administration request for $785 million in military aid for Turkey to $715 million, while keeping Greek aid at $500 million.

It also overrode administration objections and decreed that favorable interest repayment terms applicable to part of the Turkish aid must be extended to Greece in the same ratio. That means Greece will be able to repay about $300 million of the aid at a 5 percent rate.

On the population issue, the committee voted, 9 to 7, to adopt an amendment by Sen. Nancy Landon Kassebaum (R-Kan.) to ease the policy enunciated during a world population conference in Mexico last year. It bars private groups and some multilateral organizations from receiving U.S. funds because they support abortion.

Kassebaum's amendment requires U.S. aid administrators to treat such groups in a manner "not more restrictive than requirements applicable to foreign governments for such assistance." The administration policy toward aid recipients that sanction abortion requires them to maintain separate accounts so the United States can ascertain that its aid money is not being used to pay for abortions.