Arlington Commonwealth's Attorney Helen F. Fahey is investigating charges that Ronald B. Hager, a former chief deputy with the county Sheriff's Department, illegally arranged for a middleman to purchase a truck for him at a department auction while he was an employe.

Also yesterday, in an unrelated case, the attorneys handling a sex harassment suit filed by a woman employe against Sheriff James A. Gondles Jr. agreed to postpone a request for certain department documents, pending a ruling on a separate motion to dismiss the case.

The case against Gondles was transferred to Alexandria Judge Alfred D. Swersky early yesterday after all four Arlington Circuit Court judges excused themselves from the case. The judges "are all friends of mine," Gondles said yesterday.

The charges and the suit, which are unrelated, come in the middle of a hotly contested sheriff's race between Gondles, the Democratic incumbent, and the Republican-backed Hager, who resigned as Gondles' chief deputy this year to run for sheriff. Each candidate has said he is the victim of politically motivated actions.

County Treasurer Francis X. O'Leary said yesterday an investigation by his department revealed that in 1985 Hager purchased a 1979 Datsun valued at $1,312 for $25 from a Springfield man who bought the vehicle at a sheriff's auction two weeks earlier.

In a letter to Hager dated July 6, O'Leary said the purchase is in violation of the Virginia Code and the Arlington County Code of Ethics for Public Officials, forbidding employes to bid on such property or to use their positions for personal gain. He instructed Hager to turn over the truck by July 15.

Hager yesterday denied any wrongdoing.

Gondles' attorney, William D. Dolan, yesterday denied a request to make available to The Washington Post copies of Sheriff Department records sought by the plaintiff, regarding an inspection of the jail's medical standards and an evaluation of its health care services. "For now I am instructing him not to give out any documents to any sources" pending the judge's ruling, said Dolan.

Victor M. Glasberg, the attorney for the woman suing the sheriff, said the case has nothing to do with politics.

Hager acknowledged yesterday that he bought the truck for $25 from a Springfield man, but said that it was not purchased on his behalf.

"There was no intent to indirectly purchase it for me," he said. "I haven't hidden that truck from anybody, I haven't tried to deceive anybody."

On the day of the auction, Hager said he saw a man buy four vehicles, approached him later that day and asked to buy the truck.

The man who sold Hager the truck could not be reached for comment.

Fahey said she is seeking an opinion from the attorney general's office regarding any possible penalty. Hager said he would cooperate with any investigation and would turn over the vehicle if he is found to be in violation of any codes.

In the past few months, Hager has leveled charges against Gondles, alleging mismanagement of the sheriff's department and conflict of interest in giving jail-related business to a relative.

Both said yesterday they are victims of political battles. Noting that treasurer O'Leary is a Democrat, Hager said, "It's so politically motivated, it's obvious. The Democrats are circling the wagons."

Asked whether the timing of the charges against Hager were related to the election, Gondles replied, "I'm not throwing charges in this campaign, it's Mr. Hager."

Deputy Treasurer Kevin Appel, who investigated the truck purchase, said yesterday that Hager had made an "inadvertent comment" about the purchase to him in December. He said he started his investigation only recently. "When {Hager} started making charges {against Gondles}, I thought we ought to check it out," said Appel.

The truck had been seized by the county for back taxes.