WASHINGTON (AP) _ A former CIA employee who is slated to testify at the congressional Iran- Contra hearings said Thursday that he was hired in March 1986 by Richard V. Secord, a key figure in the affair, to do investigations and research.

Glenn Robinette Jr. said he traveled to Central America last fall to collect information pertaining to a civil lawsuit that was filed against Secord and 28 other defendants.

''My business association started in 1986,'' Robinette said, adding that his formal business ties with Secord ended early this year even though Robinette has done some free work for Secord since then.

Robinette, an expert in security systems, also acknowleged hiring a contractor to install a $2,000 security fence at the home of Lt. Col. Oliver L. North last summer. The Washington Post has reported that Secord gave Robinette the money for the fence, but Secord has denied that report.

North, a former National Security Council aide, is believed to have run the operation in which U.S. weapons were sold to Iran and some proceeds were diverted to the Nicaraguan Contras. Secord, a retired Air Force major general, assisted North in both endeavors.

When the Iran-Contra hearings resume Tuesday, said Robinette, who has been granted limited immunity from prosecution, he expects to be one of the first witnesses. He has given private depositions to congressional aides this week.

Robinette, in an interview, denied a report in Thursday's New York Times which quoted unidentified congressional aides as saying he would provide evidence ''directly connecting'' Secord to Edwin P. Wilson, a former CIA agent who was arrested in 1982. Wilson is serving a 52-year prison sentence for selling weapons to Libya and attempted murder.

''I have no knowledge or evidence connecting General Secord and Edwin Wilson,'' Robinette said, calling the article ''completely untrue.''

Wilson has said in interviews that Secord was a silent partner in Egyptian- American Transport and Services Corp., a now-defunct company. Secord, who testified at one of Wilson's trials in 1983, has denied having a business arrangement with Wilson.

Robinette said he knew Wilson casually from his days at the CIA but the two never had a professional association. Robinette said he had never met Frank Terpil, a former business partner of Wilson's and a fugitive from justice.

Robinette, a one-time business partner of Thomas Clines, said he met Secord in 1983 or 1984 through Clines, who was involved with Secord in selling weapons to the Contras. Clines left the CIA under a cloud in 1978 because of his association with Wilson.

One of Robinette's jobs for Secord, he said, involved collecting information from Central America relating to a civil lawsuit filed in Miami, Fla., by The Christic Institute, a non-profit organization.

The lawsuit contends that Secord and several other people in the Iran- Contra affair, including Secord's partner, Albert Hakim, and Contra leader Adolfo Calero, were involved in a conspiracy to ship weapons to the Contras.