Vice President Mondale took over President Carter's campaign appearances today and said that the president will do nothing to compromise the honor or national security of the United States in order to get the 52 hostages released from Iran.

Mondale, who said he was awakened about 1:30 a.m. with news of the Iranian parliament's meeting, talked with Carter at the White House for two hours before flying to Illinois.

Developments in Iran require that Carter be in the White House "to manage our side of that event," Mondale told his audience at Mercy Seat Baptist Church on Chicago's decaying West Side.

He said Carter was doing "everything humanly possible to secure the release of our hostages." Mondale also brought his listeners a message from President Carter that:

"He will do nothing that compromises the honor of our nation, he will do nothing that compromises the national security of our country."

The vice president made no further remarks about the hostages and repeated the same words almost exactly at a rally here in Cook County.

Mondale and his staff were anxious not to give hints of either optimism or pessimism as the president considered his options on a question that could tip the balance in Tuesday's election.

Although Mondale was a last-minute substitute and was greeted by a few signs reading, "Welcome Jimmy Carter" or "Have No Fear, Jimmy Is Here," his words were those he has used through the last weeks of his campaign.

"I'm here to plead with you to do everything you can in the next day and a half," he told the Cook County Democrats. "Please, please, vote."

At the Mercy Seat church, built as a theater in 1921 and decorated with now-peeling green and gold wall panels and once guady chandelier, the vice president told an enthusiastic, largely black audience:

"On Nov. 4, if the people vote, we win. If they don't vote, we lose."

Mondale accused Republicans of trying to discourage blacks and other poor Americans from voting.

His host, the Rev. Amos Waller, gave Mondale a message for Carter: "Tell him that we love him and we're praying for him and for our hostages."

Mondale said he asked Carter this morning what the president wanted to say had he been able to keep his campaign schedule.

Carter replied that he would have quoted -- as often he does -- Martin Luther (Daddy) King Sr. that God put everyone on earth for a purpose.

The message was to have been that a part of that purpose this week was to vote for Carter.

Although the rest of Mondale's words were his own, by standing in for the president, Mondale found his campaign transformed.

The informality that has marked his long campaign effort vanished in a twinkling of Secret Service and presidential planning.

So did his accessibility. In every city and town he has visited since Labor Day, Mondale has given press conferences. Carter, however, does not and today Mondale followed Carter's schedule.

His limousine carried the presidential seal, he stood behind a lectern with a presidential seal and the wall of Secret Service protection around him was thicker than usual. While Mondale substitued for the president here and then headed for rallies Carter had been scheduled to attend in Detroit and Philadelphia, Rosalynn Carter stood in for Mondale in Dayton and Cincinnati.

Mondale called Ronald Reagan a dangerous man to have commanding our nuclear forces and cited Reagan's opposition to civil rights legislation, but the theme that dominated his speeches was the Democrats' need for a big Election Day turnout.