A Washington car salesman was sentenced in D.C. Superior Court yesterday to at least two months in prison for attempting to bilk an elderly woman out of $500 in a new car deal.

Lawrence M. Bolet, who was general sales manager of the now defunct Senate Dodge dealership, was found guilty on Feb. 16 of "false representations" made during the sale two years ago of a 1977 Dodge Aspen to 73-year-old Ruth Blair of Southeast Washington.

Judge Leonard Braman sentenced Bolet yesterday to a jail term of from two to 15 months and ordered him to refund an $843.75 down payment Blair made on the new car, as well as $250 she has paid in legal fees.

According to the opinion, Blair and her common-law husband went to the car dealership on March 21, 1979, to trade in her 1975 car and purchase a new one. She bought a 1977 Dodge Aspen for $5,843.75 and made a down payment of $843.75, leaving a $5,000 balance. She also traded in her old car for the $2,000 needed to pay off the finance company.

Blair, who said yesterday she doesn't drive, said she bought the new car as a gift for her husband. On the same day she purchased the vehicle, her husband died, she said. The next day, she said she returned to the car dealer and asked if she could return to the new car and take back the old car she traded in.

"They told me that my old car had been sold and that the new car was already registered in my name and was considered a used car," said Blair, who cleans offices for a living.

"I would have been happy if the car dealer had given me $1,500 for both my old car and the $800 I put down on the new car," she said."But they didn't want to give me anything. They said I owed them $500 because the value of the new car had gone down."

Bolet then asked Blair to sign a promissory note to pay for alleged depreciation on her new car. Later friends urged her to complain to the D.C. Department of Consumer Protection.

But after talking with Bolet by phone, the consumer protection agency advised Blair to sign the note, according to court papers.

"The defendant knew that his represetations were false," Judge Braman wrote in his opinion. "There was no interested buyer for the car; Senate was able to treat the car as a new car on resale and the car had not depreciated $500.

"The defendant's intent, beginning on March 22, when Ms. Blair called to cancel the sale, was to defraud her," Braman wrote.

Archie Richardson, executive director of the Automotive Owners Action Council, a consumer organization that investigates the complaints of its paying membership, said he personally investigated the complaint Blair filed with his organization after she signed the promissory note.

Richardson said he subsequently found that the day before Blair signed the $500 promissory note, Senate Dodge sold her car as a new automobile to Irene Broadnix for $5,326.75, only $517 less than Blair had paid seven days earlier.