The Arlington County Board voted yesterday to pay its $1.2 million share of Metro's operating expenses from now to Sept. 30, in spite of Montgomery County Executive James P. Gleason's refusal to release Montgomery County's share of the costs.

The action effectively leaves Gleason - who has withheld funds in defane of the Montgomery County Council - alone to shoulder the blame if Metro's bus or rail operations are interrupted.

In another subway-related decision, the Arlington Board voted against making official an unofficial parking lot at the Pentagon City subway stop, near Crystal City.This means that roughly 500 cars will continue to park free in the dusty field surrounding the site.

The Board voted to pay Arlington's share of the operating costs at the urging of Board Chairman Joseph S. Wholey, who also serves on the Metro board. Wholey told fellow Board members that he is pushing a policp to heavily penalize jurisdictions that don't pay by automatically eliminating or reducing Metro service to those areas. Wholey said it would be awkard to push for that policy if Arlington withheld payment.

With Arlington's action yesterday, Gleason's refusal to release millions of dollars on both operating and construction money for the Metro system makes Montgomery County the only major jurisdiction not contributing to Metro's expenses for the first quarter of the fiscal year that began July 1, Fairfax City and Falls Church have also not paid all of their transportation subsidies, but their contributions are miruscule in comparison to Montgomery's unpaid $1.7 million.

Metro officials have said the system will run out of cash around Sept. 1, without the Montgomery County contribution.

Gleason has held the money hostage for a federal guarantee that a subway line through Wheaton will be built. That line and other parts of the proposed Metro system are under study to determine if projected construction costs can be reduced.

Although the Arlington Board voted unanimously to go ahead with the Metro operating payment, its action also included a provision tht the county get its money back if Metro service is interrupted. It makes payment beyond Sept. 30 dependent on all other major jurisdictions agreeing to pay their share.

For now, "I think it is in our best interest to pay," said Wholey. Wholey said he supports a policy that would call for automatic bus and rail service cutbacks to jurisdictions that withheld money. His policy also would trigger public hearings on the prospective cutbacks. The Metro board has the power to cut back service now, but the action is not automatic and has never been taken.

Insuring such penalties "would have the effect of pushing Montgomery County around to pay," said Wholey, "we're playing games," he said, although he quickly amended the statement to place the blame on Gleason, not the Council.

On the Pentagon City parking lot question, the Board voted 3-to-2 not to accept a recommendation from County Manager W. Vernon Ford to allow a parking facility to be operated in an area where hundreds of commuters now park daily without official sanction.

County staff members had approached the Cafritz Company, owners of the vacant field that surrounds the subway station, and worked out an agreement to provide a commercial parking lot on the site unitl 1980, when stations farther out on the line would be opened.

The Board rejected that arrangement after hearing objections from the County Planning Commission and from citizens who argued that sanctioning parking would add to traffic congestion and pollution in the area and lure riders away from connecting bus service.

"It's one more way in which the environment would be adversely affected," said John H. Quinn, of the Pentagon City Coordinating Committee, which opposed the establishment of a lot. "This proposal will discourage the use of an integrated transportation system," he said.

The number of cars parking in the rutted field near the subway stop has steadily increased since the station opened in July. Most recent counts show about 550 cars parked on the unimproved area and about 90 on the nearby streets.

Approximately 40 per cent of these cars are from Arlington, about 20 per cent are from Alexandria and 20 per cent from Fairfax County, according to transportation director H.S. Hulme Jr. About 5 per cent are from Virginia counties outside the metropolitan area, and another 15 per cent are from out of state, apparently including a number of cars belonging to tourists who ride the subway downtown to sightsee.

The Board's rejection of the official parking lot plan, under which commuters would have been charged, leaves the situation basically unchanged, said Hulme. The county's zoning administrator might take action to bar parking as a violation of the zoning ordinance that covers the land, but so far there has been no request to do so, Hulme said.

Wholey and Board member Walter Frankland favored making the parking lot official. Frankland said he believed that most of the people who park there are probably not bus riders who have been lured from mass transit. "I don't think it's immoral . . . to drive and take the train," said Wholey, Board member Ellen Bozman indicated she would like to review the idea again after bus routes she would like to review the idea again after bus routes are altered to drop more people at subway stops.