Furnace repair in Preston typically costs around $300 on average. The majority of homeowners pay approximately between $102 and $823. Owners can pay as low as $50 and as high as $800. A lot of factors, on the other hand, can affect the total cost of your furnace repair service. If your furnace is covered by warranty or some of its parts are, the cost can be lower. However, if it is already past the warranty period, the cost of the furnace repair service will generally depend on the scope of the damage to be repaired. A damaged heat exchanger or wiring problem is costlier to fix mainly because these parts have to be replaced.