BALTIMORE (AP) _ Some 35,000 depositors of First Maryland Savings and Loan face another 90 days without access to their money after a judge appointed a conservator for the troubled thrift.

The order Wednesday by Circuit Judge Joseph H.H. Kaplan bans withdrawals and limits interest rates on most accounts to 51/2 percent.

He turned over operation of the thrift to the Maryland Deposit Insurance Fund, created last May after Gov. Harry Hughes declared a state of crisis in the Maryland savings and loan industry, placed two of the 102 privately insured thrifts in conservatorship and limited withdrawals at the rest to $1,000 per account per month.

The Deposit Insurance agency manages a state fund that insures deposits up to $100,000 per account for the 65 former privately insured thrifts that have not gotten federal deposit insurance.

Fifteen S&Ls remain subject to some kind of withdrawal limits. The others are operating without restrictions, either because they obtained federal insurance or were exempted from the governor's order after a federal audit showed they were sound.

Melville S. Brown, fund director for MDIF, said he will seek a buyer for First Maryland, a Silver Spring-based thrift with $400 million in assets.

Wednesday's action was taken after MDIF became convinced First Maryland would not be approved by the Federal Home Loan Bank Board for coverage by the Federal Savings and Loan Insurance Corp.

Officials of First Maryland made their final pitch for federal insurance Wednesday before the hearing that placed the thrift voluntarily into state conservatorship.

''They weren't given any indication that they would be given conditional approval'' for FSLIC coverage, Brown said. ''The examiners have repeatedly recommended strongly that First Maryland not be given FSLIC approval.''

First Maryland had signed a preliminary takeover agreement with a Citicorp subsidiary in September, but the agreement collapsed last month.

Kaplan's order, which extended the freeze on withdrawals that had been in effect at First Maryland for the past 90 days, gives MDIF some breathing room in its efforts to sell the thrift.

The General Assembly in emergency legislation last spring set a Dec. 31 deadline for mandatory liquidation of large thrifts, including First Maryland, unless they could obtain federal insurance or find a buyer or merger partner.

''This is sort of in lieu of finding a buyer,'' Kaplan said after the hearing. ''They're not going to be able to liquidate the assets or find a buyer'' by the end of the year.

The state is allowing limited withdrawal of funds in hardship cases at two other thrifts where deposits are frozen. First Maryland likely will be brought under that plan within a few days.

Under Kaplan's order, the limit on interest rates at First Maryland applies to all accounts except certificates of deposit, which will collect interest at the contract rate until they mature, when they will be rolled over at 51/2 percent interest.