When Rep. Henry B. Gonzalez (D-Tex.) received a $4,000 campaign contribution from the home-building industry last week -- two weeks after an election in which he had no opponent -- it did not take him long to figure out why.

"I can only conclude that the contribution was intended to assure 'access' in the future," Gonzalez wrote in returning the money to the National Association of Homebuilders' political action committee. " . . . I can't help but feel . . . that the late substantial contribution from BUILDPAC had everything to do with my continuing role as the likely chairman of the housing and community development subcommittee in the new Congress."

Gonzalez is something of an oddity in a city where most lawmakers have grown addicted to PAC money. He does not hold Washington fund-raisers. He spent a total of $43,787 on this year's campaign. He clings to the almost archaic belief that a congressman should not accept big donations from the groups that seek to influence his committees.

Gonzalez told the builders that they must have had second thoughts about sending the check, which was dated Oct. 18. "I cannot help but wonder if your organization would have contributed at all if I had faced a Republican opponent," he wrote.

Robert D. Bannister, secretary of the home-builders' PAC, said the group voted Sept. 25 to include Gonzalez in a list of 408 congressional candidates who received $1.8 million in donations. He said the check was mailed Oct. 18 to the group's Texas trustees, who tried to find the right person to present it to Gonzalez.

Bannister said the trustees finally gave up and mailed the check the day before the election.

"Our philosophy is we support the candidates who are supportive of housing issues," Bannister said. "We've had a good relationship with the chairman. We deal with him all the time. If we didn't have access now, this certainly wouldn't do it."

In a telephone interview from San Antonio, Gonzalez called the donation "a calculated attempt to influence future behavior, whether it's access or amenability to the views and aims of the home-builders." He said that while he is a strong housing advocate, the group regards him as insufficiently supportive of the Reagan administration.

"They feel I haven't parted my hair exactly as they would have wished," he said.

Gonzalez said the incident reminded him of the day after he was elected housing subcommittee chairman in 1981, when a housing group rushed to deliver a $3,000 donation. Gonzalez refused to accept it.

"I've been very concerned about the complete domination of these special interests on the committees I belong to," Gonzalez said. He said he did not want "an enormous obligation to one particular contributor" that might seek future legislative favors.

"You will have as ready access to me as anybody else," Gonzelez assured the home-builders in his letter.