It was 1970 and the United Farm Workers, under the guidance of Cesar Chavez, had turned a national grape boycott into one of the most extraordinary labor victories in U.S. history. The union was poised to revolutionize American agriculture.

Almost all California table grapes came in crates bearing the union label. Union leaders were discussing ways to organize the million nonunion farm laborers throughout the country. Grape growers were exhausted and demoralized after spending millions in an unsuccessful effort to stop the boycott and the strike.

Eleven years later, the growers are waxing triumphant while the union is in difficulty. The United Farm Workers no longer control the majority of grape contracts. They have signed contracts in only two states outside California.

Their central leadership here, having exchanged its headquarters near Delano for a refurbished mountain sanitarium, has been hit by defections, charges of mismanagement and a growers' counterattack of increasing force, wealth and sophistication.

The union's troubles, like its triumphs, again throw a spotlight on Chavez, a 54-year-old dynamo with a seventh-grade education who still has a hold on the loyalties and imaginations of his admirers. Chavez fasts often, lives in a four-room, wood-frame cottage and insists that he and other union officials draw no salaries.

His supporters say Chavez is pushing to make the union modern and efficient. His critics say he is the one, because of personal paranoia, who is holding the union back.

In an interview, Chavez acknowledged his union's political and financial problems, but said his critics had made too much of the problems and his alleged sensitivity to criticism. "This union is growing quite fast, but it is true that they are not seeing it," he said.

Without doubt, Chavez is responsible for fundamental improvements in the lives of American farm workers. California rural laborers, who earned an average of $1.40 an hour in 1965 with no fringe benefits, earned an average of $4.51 an hour in 1980, with many union contracts providing $6 an hour plus health care, paid holidays and pensions.

But that very success, forcing a rise in wages at even nonunion farms and making workers less desperate for change, has weakened the ability of Chavez's union to grow.

Chavez himself chooses to put it all in dramatic personal terms. In a recent speech he said the union was facing "the greatest dangers of its history" and blamed "malignant forces, organized clandestinely . . . that are jointly struggling to destroy our union."

He includes among those "malignant forces" the growers and the Teamsters union, with whom Chavez signed a peace treaty in 1976. In a bitter feud, the Teamsters had wrested away most of the grape-picking contracts the union had won.

But Chavez denies charges that he also feels threatened by top lieutenants who have recently left the union leadership.

Some of his remaining aides, Chavez conceded, may have accused their former colleagues of disloyalty and of trying to start a rival union in the Salinas area. But he dissociated himself from such "ridiculous" charges, saying, "I was not involved in them and I am not going to be involved."

Supporters and critics of Chavez dispute just how much he or anyone can be blamed for the failure to organize more of the nation's farm workers. Chris Hartmire, a 49-year-old Presbyterian minister who became Chavez' assistant after years as head of the California migrant ministry, said 105,000 workers are now covered by United Farm Workers contracts, compared with 67,000 in 1973, just before the union's hold on grape picking was destroyed by the grower-Teamster alliance.

An official union report in September says only 30,000 "regular dues-paying members," but Hartmire discounts that figure, which, he says, appears to includes only members who pay dues year-round and ignores the majority covered by seasonal contracts.

Whatever the membership totals are, they are being nibbled at by decertification elections organized by clever growers and disgruntled workers. And union leaders cringe at the threat of a Republican, grower-backed replacement for the union's most important political friend, Gov. Edmund G. (Jerry) Brown Jr.

"It's going to be difficult for us" if that happens, Chavez said.

In September, the first outspoken opposition to Chavez since the union organized in 1962 led to a walkout by 30 to 50 of the 350 delegates at the union's Fresno constitutional convention.

"They want to run the union like a movement," said Jose Renteria, director of the union's Salinas office and a leader of the walkout, "and we want them to run it like a union." Renteria said the union had cut off his medical benefits in retaliation for the walkout, and he had since resigned.

Chavez said he could do what his Salinas critics suggest--put more union representatives on salary in order to strengthen organizing efforts--"but this union doesn't raise enough money from dues to pay people."

"They don't understand," he said. "We don't raise enough money because so many of our members are seasonal workers and pay dues only seasonally."

After the loss of the grape-picking contracts in the grower-Teamster raid of 1973, the United Farm Workers began to organize pickers of vegetables, citrus fruits, tomatoes and other crops. But by rebuilding membership in this way, the union increased and enormously complicated its administrative load.

"One of the problems of growth and success and getting contracts is that they get an increasing load of administrative responsibilities and can get overextended," said Herbert A. Perry, acting chairman of the state Agricultural Labor Relations Board.

The board, the only one of its kind in the United States, accepts some of the blame for the union's problems. Understaffed, it has been slow in processing unfair-labor practice complaints, further eating into union officials' time and slowing the organization's growth.

At Cattle Valley Farms in Coachella, union missteps led workers to begin an effort to decertify their chapter of the United Farm Workers.

Jim Boston, a 35-year-old mechanic with a wife and four children, said he was grateful for a job at the 3,000-acre cattle, wheat, cotton and tomato farm a few months ago, after the tractor company he worked for folded. But in September the company informed him and 43 other employes that it had signed a UFW contract and they had five days to sign their union cards or be fired.

"All of a sudden we find out we're going to have to give 2 percent of our pay as dues to these people and we don't know the slightest thing about the contract," Boston said.

The vote to accept the union came in 1978, before most of the farm's current employes had been hired, and the union has not done a good job keeping new workers informed. The union shop steward spoke only Spanish, making it difficult to communicate with workers like Boston, who speaks only English.

Within a few days, Boston and two dozen other workers had conducted a short strike to protest the UFW contract. Most of the protesters were Mexican Americans, like the vast majority of UFW members, but they were upset that the new union dues would mean smaller paychecks for many of them.

Boston complained that the union would gain the right to force a worker out of a job if he were not in "good standing" with the union. The switch to union health insurance, he said, would leave them without coverage for a month. Furthermore, somebody was harassing the contract resisters, breaking a car windshield and poisoning one of the worker's dogs.

The union's 23-year-old Coachella field director, Saul Martinez, tried to pacify the group.

"It's true that a lot would be earning less, but the company was cutting down the hours they were working, in order to create discontent among the workers," he said. He denied there would be any gap in health coverage and insisted that mechanics like Boston, who backed the revolt most enthusiastically, could elect their own bilingual shop steward once they joined the union.

The farm's 35-year-old owner, Peter Solomon, said he had spent $300,000 on legal and settlement costs for the union contract and now found he still had a strike. "I wish I could crawl into a hole," he said.

When Boston and others told him they would stay off work unless he sided with them, he referred them to attorneys working with the Western Growers Association, an anti-Chavez group. The attorneys helped arrange a decertification election.

The uncounted ballots are now being held pending court action by the union, which charges that Solomon created the worker dissent by systematically firing his most pro-union employes. Solomon denies it, saying the union trumped up charges after he fired some employes for bad attitude and incompetence.

Meanwhile, there are the union's continuing problems with the growers. Already powerful as owners of the state's number one industry, the growers have united into a formidible political machine.

One experienced state politician, requesting that his name not be used, said that in the decade since Chavez' grape boycott victory, "the growers have become first or second in the state in their capacity to raise money and contribute to political campaigns. They can outspend the union 20 or 30 to 1 in terms of legal talent."

Chavez shruggs this off. "If you go back and take the old days, what the struggle was like then, the growers are not doing that well now in keeping the union out," he said.

Th growers' principal foe, other than Chavez, has been Brown, who pushed through and signed a farm labor law that requires worker votes on union representation. The Teamsters, with the growers' cooperation, were able to take over most of the UFW grape contracts in 1973 because no such law was then on the books.

Brown, however, will leave the governorship next year to try to enter the U.S. Senate. Although his most likely successor, fellow Democrat Tom Bradley, is pro-union and is leading in the polls, a victory by a pro-grower Republican, either Attorney General George Deukmejian or Lt. Gov. Mike Curb, is not impossible.

Only Brown's veto, people on both sides of the issue say, has prevented serious weakening of the farm labor law. Grower resistance helped kill two Brown appointments to the Agricultural Labor Relations Board. Two followup appointments were just barely approved.

To Hartmire, the most successful grower efforts have been in "going to labor attorneys and labor consultants, using sophisticated legal strategies to stall contracts." Long delays between union votes and actual contracts cost money and, as happened at Cattle Valley Farms, create worker resentment against the union.

At Santa Clara Produce in Oxnard, Hartmire said, the workers voted for the UFW in October, 1975, but the union has managed to negotiate a contract only in the past few weeks, six years later.

Pressures from the union's well-financed opposition has done nothing to improve the atmosphere 3,000 feet up in the Tehachapi Mountains, in a remodeled tuberculosis sanitarium renamed Nuestra Senora de la Paz (Our Lady of Peace, usually just called "La Paz") that is now union headquarters.

The union moved there, Hartmire says, to allow its local organization in Delano to run its own affairs and to focus the efforts of Chavez and his top assistants on organizing other parts of the state and country. About 180 staff members and their families are housed in the complex.

The dissident Renteria argues that the move to the mountain retreat 30 miles from Bakersfield "cut Cesar off from the real world."

Others say that controversies about missuse of funds and staff defections, including the departure of leading union organizer Marshall Ganz and legal department head Jerry Cohen, were the result of personality conflicts, differences over strategy and the personal financial problems expected in any large organization.

Only lately have Chavez and his critics begun to hurl more serious, so far unproved, charges at each other, such as that Ganz and others are trying to set up a rival union in the Salinas area, or that Chavez's Hispanic lieutenants resent the influence of Jews at the headquarters.

Marc Grossman, 32, who handled press for Chavez for six years before recently accepting an legislative staff job in Sacramento, said, "Like any organization, there are a lot of personalities, and some conflict, but maybe less than a lot of other unions."

Grossman said his own departure was for personal career reasons and he remained an admirer of Chavez. Even Chavez's severest critics, such as Renteria, still seem to hold the union president in esteem.

Some of the union's problems, Grossman suggests, may arise from Chavez's own restless ambition to keep his union up with the times, able to counter the latest blows from the growers. The union's offices are now linked by microwave telephone; a $300,000 computer has been purchased, and a 24-hour radio station is planned in January.

"When I was there," Grossman said, "Cesar was usually the one making the effort to adopt new strategies--and meeting a lot of resistence. Change comes slowly and with a lot of pain, for people who are used to doing things in a certain way."