The Federal Communications Commission yesterday upheld its earlier decision ordering the television networks to sell President Carter's election committee a "reasonable" amount of air time next week for the president's announcement that he will seek renomination next year.

Voting 4 to 3 along the same party lines as in its first vote last week, the commission turned back appeals from the three networks, which had argued that the request was for too much time and too soon.

The networks are concerned that there will be a deluge of candidates seeking large chunks of air time during critical competitive broadcasting periods.

ABC and CBS immediately filed papers in federal court seeking a review of the FCC order and a stay until the issue is resolved. NBC is expected to file a similar appeal today.

In its filing, CBS said the FCC was giving candidate more rights than they are supposed to have at the expense of the licensed broadcaster. At the same time, CBS said, although a majority of the commission voted against the networks based on the FCC rule on "reasonable access," at least one member of the panel's Democratic majority, James Quello, said he doubted the constitutionally of the regulation.

Consequently, CBS argued, the FCC and the courts should evaluate the constitutionally of the rule before enforcing it.

The Carter-Mondale Presidental Committee originally sought to purchase from one of the networks a half hour of air time on any of four nights next week.

Both FCC Chairman Charles Ferris and Democratic commissioner Tyrone Brown said they hoped yesterday's vote would lead to talks between the networks and the Carter people.

"Both sides in this case wanted the commission to tilt the balance their way," Brown said in an interview. "But we did not do that. The only way you can ultimately solve this problem is to have the broadcasters and the candidates sit down and negotiate."

Ferris agreed, contending that the case sets no precedents because "every one of thes cases has to be handled on its own merits." Both Brown and Ferris said any statue requiring "reasonableness" would always have to be applied on a case-by-case basis.

Sources at Carter campaign headquarters said the networks had informed them they would now discuss the potential sale of air time to the election unit.

It was still unclear whether Carter would be able to buy his half hour on one of the nights requested. The networks are required only to offer a "reasonable" deal, and in any case, the court could tie the matter up until after next week.

In their court motions, the networks asked that the issue be considered on an expedited basis.