The Fairfax County Board of Supervisors, wielding the only tool Virginia law provides, temporarily denied a developer's request to convert 343 rental apartments and town houses to condominiums.

The supervisors ordered more hearings and studies of the conversion request on the ground that the Arrowhead Apartments near Tysons Corner do not have enough parking spaces to satisfy county zoning laws.

The board also reached a truce with its semi-independent housing authority yesterday. The county announced that the authority had agreed to abandon a proposal for a controversial public housing project in Springfield, known as Coventry. At the same time, the board voted to support the authority's efforts to build a similar project in Centreville.

Virginia law requires that condominium developers bring their apartments up to modern zoning standards, but does not require them to seek approval from or help provide for current tenants.

The supervisors, who a month ago were leaning toward a flat denial of the developer's request at Arrowhead, said privately last night that they were reluctant to make a final decision while the General Assembly is considering a bill that would strip them of the only control they have. The bill, introduced by Del. John Rust of Fairfax, would relieve developers of the need to conform to all zoning laws when they convert, the supervisors said.