The Fairfax County Federation of Citizens Associations, striding into an election year mine field, has voted in favor of increasing county supervisors' salaries by $2,500 a year over a four-year period.

The federation's support last week for the raises, which would increase salaries from about $22,500 in 1984 to $32,500 by 1988, comes just three months before the April 15 date by which, under state law, the supervisors must approve a raise if it is to go into effect for the next four-year term. All nine supervisors are up for reelection this fall.

The problem is that, although the total $10,000 raise would bring Fairfax supervisors' pay more in line with the $34,000 salaries paid council members in Maryland's Montgomery County, a jurisdiction of similar size and wealth, not all Fairfax County supervisors favor the idea.see it as a move to make the part-time job of supervisor a full-time one. (The job is considered part-time in Montgomery.)

In fact, more often than not the job is full time, some supervisors say. Springfield supervisor Marie B. Travesky, who estimated last week that she spends 60 to 70 hours a week on board matters, said she thought both "the board and the county need to take a hard look at what the job entails. If you keep it on a part-time basis, you're eventually going to limit it to retired people or housewives." She favors an increase in pay to make it possible for more county residents to consider running for office.

But board Chairman John F. Herrity used a similar argument last week against increasing the supervisors' pay.

"I have a deep philosophical problem here: Whether you say you're full-time or part-time, when you start making what normal, two-legged people make for a living, they expect you to work full time," he said. "Unfortunately, I can't just walk away from my insurance company and $40,000 to $50,000 for four years . . . and send my three kids to college. And neither can a doctor or a lawyer or a businessman. If you make it full-time, you'd be limiting the field to retired people and people without jobs."

Both Herrity and Annandale supervisor Audrey E. Moore declined a previous pay raise and earn about $18,000 a year as supervisors.

At their current annual salary of $22,500, Fairfax County's supervisors already are the highest paid in Northern Virginia. In Prince William County, for instance, supervisors earn $10,000 annually; in Loudoun County, $6,000; and in the city of Alexandria, $12,000. Arlington County's chairman earns $11,340; all other Arlington board members earn $10,206.

Such regional disparity further clouds the prospect of a substantial raise. Travesky, for instance, said she believes that a $10,000 increase would be excessive. "I don't think it would go over very well," she said. Herrity agreed, saying that, for a raise to have a chance before the board, something "far more modest" is in order--"something along the lines of what county employes are getting," which is between 3 and 6 percent.

But there is another obstacle in the way of the raise: some supervisors are rumored to be opposed because a raise might encourage others to run against them.

"The argument I have heard some supervisors make is that, if you keep the salary rate down, you won't have as many candidates," said Travesky. The federation's resolution calls for increasing the wages "in order to encourage all qualified candidates to seek election to the board without undue personal sacrifice."

But Herrity dismisses the better-pay, better-supervisors argument as "baloney."

"Supervisors are supposed to be policy-makers, not administrators," said Herrity. That makes them part-timers, he said. The real administrator, Herrity pointed out, is Fairfax County Executive J. Hamilton Lambert who, according to a county spokesman, earns $73,500.

"We pay some pretty good salaries to the folks who sit across the river on that Hill, and I've never noticed that it made a hell of a lot of difference," said one member of the federation during last week's debate. "But I guess hope springs eternal."