Some people have a conscience; others, a conscience has them. Bill Gandall, 77, a retired labor organizer who lives in Juno Beach, Fla., is in the second group. He spent eight days recently in Nicaragua as part of a delegation of North Americans that presented 15 ambulances to the Sandinista government. Gandall helped raise $200,000 for the ambulances, which were shipped from Japan to Managua.

It was Gandall's second stay in Nicaragua. The first came in 1928 when, as a teen-aged Marine, he spent two years fighting Augusto Cesar Sandino, the leader for whom the Sandinistas are named. "We never caught him," Gandall recalls, "because no matter how we tortured, we could never get people to inform."

As a Marine in Nicaragua, Gandall remembers the fervent way the corps spread U.S. democracy: "I shot a guy at the polls" in the fraudulent election of 1928. After that, it was "taking part in rapes, burning huts, cutting off genitals. I had nightmares for years. I didn't have much of a conscience while I was in the Marines. We were taught not to have a conscience."

The teaching didn't last long. Gandall left the Marines in his early twenties and went into union organizing. "That woke me up," he says. Another jolt was realizing the uselessness and destructiveness of current U.S. military intervention in Nicaragua: "It's a disaster to support the contras because they are mostly led by former Somoza people. I saw some of the atrocities committed by them. They learned from the Marines and carried on our work."

The efforts of Gandall -- a man prodded by his conscience to make reparations -- are a positive contrast to the drive by the Reagan administration to rearm and refund the contras. As much as $130 million is expected to be requested. The significance of someone like Bill Gandall is that he represents the third -- and usually hidden -- side in the debate. He is one of a large number of North Americans who, while opposing the waste of money on the contras, is working to increase personal nongovernmental aid to the Nicaraguan government.

The breadth of the movement is seldom reported.

A freighter is now sailing from a port in New Brunswick, Canada, to Nicaragua loaded with 560 tons of clothing, medical supplies, corn, grain, books, fishing equipment and other goods. A major force behind the shipment is Bernard Sanders, the socialist mayor of Burlington, Vt. About two years ago, wanting to go beyond mere complaining that funding the contras was neither moral nor practical, Sanders persuaded the citizens of Burlington to commit themselves to their own foreign-aid program.

The mayor, stating the obvious, which seems to keep being forgotten, said: "Instead of invading Nicaragua and spending tremendous amounts of tax dollars on a war there, money which could be much better used at home, it seems to me that it would be worthwhile for us to get to know the people of Nicaragua, understand their problems and concerns, and see how we can transform the present tension-filled relationship into a positive one based on mutual respect."

In addition to $300,000 worth of goods from Burlington, the freighter is carrying 75 tons of clothing and food from Church World Services, 30 tons of clothing from Catholic Relief Services, 127 tons of food from the Mennonite church and 300 tons of corn and beans from the Canadian food-grain bank. The boat is sailing from New Brunswick because no U.S. firm was willing to buck the embargo.

On land, coordinators of "Quest for Peace" announced last week they are halfway toward their goal of collecting $27 million in humanitarian aid for Nicaraguans. "Quest for Peace" is a national campaign based in Mount Rainier, Md., and cosponsored by an ecumenical coalition of religious groups. It was formed in December 1985. The Rev. William Callahan, a Jesuit priest, echoes the thoughts of the mayor of Burlington: "U.S. citizens are fed up with the illegal policy of our government toward Nicaragua which has made the United States an international outlaw. They are determined to act in true democratic and Judeo-Christian ways to heal the wounded, clothe the naked and help shelter Nicaraguans attacked by the U.S.-backed 'contra' terrorists."

The $27 million is an unofficial matching grant for what Congress voted the terrorists in June 1985. Last week, Reps. James Jeffords (R-Vt.) and Peter Kostmayer (D-Pa.) released an investigative report commissioned by the Washington office on Latin America. About the contras, the report documented "a pattern of indiscriminate attacks against civilian targets, kidnappings, rapes, assassinations, mutilations and other forms of violence."

According to Bill Gandall, that's the story of the Marines in 1928. The difference between then and now is that the United States paid American kids to brutalize Nicaragua. Now we pay Nicaraguans directly. Either way, Gandall's conscience won't be still.