A small number of Arlington homes have been assessed incorrectly over the last two years because of a computer problem, but corrections are now being made, the county assessor said last week.

James R. Vinson, county director of real estate assessment, said about 5 percent of the 39,000 homes and business in Arlington were affected. Most were new homes in older neighborhoods or old homes in newer neighborhoods.

[WORD ILLEGIBLE] problem was caused by the computer program when it registered increasing neighborhood property values. The program would add a percentage increase to the value of the home rather than apportion some of the increase to the value of the land, Vinson said.

For instance, Vinson said, if a lot is worth $35,000 and the house is worth $65,000, then the entire residence would be appraised at $100,000. But if the appraisers found that similar houses in the neighborhood were selling for about $105,000, they would consider their assessments too low and would program the computer to increase the appraised values of the neighborhood by 5 percent, he said. The problem with the program, however, was that the computer increased the value of the house - the largest part of the total assessment - by 5 percent, rather than increase the entire value of the residence, which includes the land assessment, he said.

The problem most often affected neighborhoods where there are houses of different ages, Vinson said. It caused newer homes to be overassessed and older homes to be underassessed.

Vinson said his staff is working to correct the problem by making individual examinations of the areas where it is believed to have been most inequitable. The six county appraisers began the work this year, and the changes will be reflected in 1978 assessments to the Addison Heights, Aurora Hills, Lyon Park, Lyon Village and Cherrydale neighborhoods. Over the next two years the appraisers hope to complete the work throughout the county, he said.

Persons who have been assessed incorrectly can appeal the assessment. The county, however, does not plan to give refunds or require additional payments on the incorrect assessments.