The Arlington County Board decided Saturday to postpone action on proposals to modify a county ordinance that restricts county employees' political activities. But at the same time, a majority of the Board indicated that they will oppose any major changes in the county's "little Hatch Act."

Unions and associations which represent county employees had petitioned the Board to review and revise the Arlington County Code's limitations on political activity and protections from political coercion. The ordinance covers about 2,500 workers.

Among the restrictions the code imposes is a prohibition against running for local and state office. Other parts of the code, which were written as protections for public employees, have sometimes been interpreted as denials of rights.

For instance, said Board member John Purdy, who supports modification, a provision that says employees are protected from infringement on their right to express opinions in private, has been interpreted as limiting public expression of opinions including bumper stickers.

Like the Hatch Act, federal legislation which may be repealed, the Arlington ordinance was written to protect public employees from being strongarmed by public officials and to minimize problems of political patronage.

"We are of the opinion that the intention of the code is the protection of employee rights. The fact is, certain sections of the code deprive us of our rights," wrote representatives of five employee groups, urging review.

"Our position is that we should be protected from being coerced into political activity, but the restriction on our voluntary political activities should be amended," they said. The groups are the Association of Professional Clerical Workers, Council 30 of the American Federation of State, County and Municipal Employees (AFL-CIO), the Arlington Professional Firefighters Association, the Arlington Firefighters Political Action Committee and the Arlington Police Benificiary Association.

"I'm very skeptical that we should make a change," said Board chairman Joseph S. Wholey, who said he might nonetheless be persuaded on some items. Besides Wholey, Board members Dorothy Grotos and Walter Frankland appear likely to oppose changes.

"My general position is that the Hatch Act is a good thing, and that Mr. Carter and the Democrats are going in a bad direction (in attempting to change the Hatch Act)," he said. The Democratic platform calls for removing the Hatch Act's restrictions on partisan political activity.

The Board is expected to consider the county code's political activities section again after the county attorney has had a chance to review the constitutionality of some portions of it. No representatives of the employee groups were on hand for Saturday's hearing.

In othe action, the board approved an appropriation of $80,000 for an expository writing program for the Arlington public schools. The program, designed to help correct what some educators consider a widespread inability of high school graduates to write clearly and grammatically, would measure student growth in writing skills at grades 5, 8 and 12, and improve the programs designed to teach writing.