An Arlington Circuit Court judge ruled last week that the county could not ask Ronald B. Hager, a former chief sheriff's deputy and a candidate for sheriff in last November's election, to return the truck he purchased from a man who bought the vehicle at a Sheriff's Department auction.

Judge William L. Winston also dismissed two of the three counts contained in a civil suit against Hager filed by the Arlington Treasurer's Office pertaining to possible fraud on Hager's part. It let stand for possible trial the treasurer's allegation that Hager breached the public trust in purchasing the vehicle.

The judge made his ruling after Hager's attorney filed a motion to dismiss the case. A trial date has not been set.

Hager, who ran unsuccessfully against incumbent Sheriff James A. Gondles Jr. last fall, bought the truck in 1985 from a man who paid $25 for it at the auction. The truck, which was assessed at $1,312, had been confiscated by the Treasurer's Office because its owner owed $189.95 in back taxes.

In July, in the midst of a heated political campaign, Treasurer Francis O'Leary, who publicly supported Gondles, filed suit against Hager, alleging that he illegally purchased the truck.

Hager denied the charges and refused to turn over the truck.