The Redskins forgot a season of turmoil and heartache for three hours yesterday. For a change, they had some fun, and in the process of devastating the stunned San Diego Chargers, 40-17, they took a major step toward saving Coach Jack Pardee's job.

Pardee has been saying for weeks his players are on the verge of breaking out of their long losing streak. Finally, they did, after five straight defeats. These were the Redskins of last season, opportunistic on defense and versatile enough on offense, with Joe Theismann throwing a pro career high 26 completions, to embarrass the high-flying Chargers before an RFK Stadium crowd that probably couldn't believe what it was witnessing.

If the Redskins somehow can repeat this performance in the final two games against the New York Giants and the St. Louis Cardinals, it would make it extremely difficult for owner Jack Kent Cooke to fire Pardee, who has been under extreme pressure.

Cooke, who had decried what he saw as a lack of spirit, was overjoyed, although he declined to comment, on Pardee's future as the Redskin's coach.

"I had a wonderful day, a wonderful day," he kept repeating after his team had recorded only its fourth triumph in 14 games with a show of enthusiasm and hard hitting that would have warmed any owner's heart.

The Redskins had scored only 51 points in their last five contests. But against the Chargers, they easily could have run up at least another 12, and maybe more.

But on a day when the defense intercepted five passes -- Joe Lavender picked off three -- forced two fumbles and harassed Charger quarterback Dan Fouts into his worst game of the season, the offense was almost forced to do well.

For once, however, the Redskins didn't need that much help to score. In running up their highest point total in five years, they outguessed the Charger defense at almost every juncture with a mixture of short passes and quick runs. And the Redskins got a big boost with the return of Theismann, who played despite a very sore hamstring that probably should have kept him on the bench.

Theismann, who sat out last week, completed 26 of 37 passes for 269 yards and two touchdowns. But he had plenty of help. His offensive line, which had been struggling for weeks, limited the Chargers, the best in the league at dropping quarterbacks, to three sacks while controlling the line of scrimmage. And fullback Clarence Harmon, taking advantage of San Diego's inability to cover backs in the secondary, caught a team-record 12 passes for 112 yards.

"Everywhere I looked out there, we were having fun," Harmon said. "It was a great sight. This has been a struggle for all of us, and we needed a day like this, when everything went right. Why? I wish I knew, because if I did, we wouldn't have the record we have.

"But we knew that this was on national television and we had nothing to lose. Why be tight about it? We wanted to show people we could keep up with a team that can score like the Chargers. We didn't want to embarrass ourselves."

Theismann claimed the Redskins didn't have "one new play or call, something we haven't used before this game." But the offense certainly looked different. Washington was the second lowest scoring team in the NFL entering this contest and had just four touchdowns in the last five weeks.

Added Harmon, "The defense has played well enough the last two weeks (giving up only 24 points) for us to win. The offense knew that. We knew if we improved, we could start winning."

This time, both units were outstanding. Fouts had been averaging 296 yards passing and 22 completions a game directing the league's best offense. But he was limited to a so-so day for him: 13 of 25 for 200 yards and four interceptions.

Fouts should have realized it wouldn't be his afternoon when on San Diego's first possession, he was intercepted by Lavender, who returned the pass 51 yards for a touchdown. In practice during the week, Lavender had made a couple of interceptions playing against the formation the Chargers used on that play. Fouts had gone three games and 89 passes without being picked off.

But Lavender was just getting started. On San Diego's next possession, receiver Charlie Joiner had a second-down pass bounce off his hands and into Lavender's arms. The veteran cornerback returned that one to the San Diego 31. Although a Charger sack eventually forced a punt, the Redskins actually tried a long pass, a part of the offense missing for weeks, during that series.

The Redskin line was giving Theismann time to throw for a change and it paid off later in the quarter. He directed a 63-yard scoring drive, highlighted by a 27-yard pass to Wilbur Jackson, who had six receptions. Jackson got the touchdown when, as Theismann scrambled, he shook loose in the right flat, broke a tackle and went in from 18 yards out.

After a six-yard pass to tight end Greg McCrary drew San Diego to 14-7, the Redskins set up the first of Mark Moseley's four field goals, this one from 28 yards, after a scoring pass to Ricky Thompson was nullified by a holding penalty on George Starke.

The Redskins completely wasted two other breaks. Tight end Rick Walker fumbled at the Charger three following a pass reception, a sack by Dave Butz having caused Fouts to fumble at the San Diego 21. Then, after Lavender got his third interception on an overthrown pass, Jackson fumbled the ball right back on first down at the Charger 37.

That was the end of Washington's giveaway program. Moseley and Rolf Benirschke exchanged 26- and 45-yard field goals, respectively, before the half ended, then San Diego threatened to close the gap to 20-17 with a march to the Redskin four to open the third period. But linebacker Monte Coleman, who was burned on the McCrary touchdown, intercepted Fouts in the end zone and ran out to the 39.

The Redskins turned that into a 46-yard Moseley field goal. Moments later he kicked another from the 46 after a short Charger punt. But he missed from 56 and San Diego quickly pulled to 26-17.

Washington needed one more score to put the game away, and got it with Theismann's four-yard pass to Ike Forte on the ensuing series. The touchdown came after San Diego's Wilbur Young popped offside on a fourth and one at the nine with the Redskins in field goal formation.

Forte later scored from the three after Theismann called an audible with 7:03 left in the game. But long before then, the Redskin bench had started celebrating.