If a furnace owner wishes to replace only the furnace and not the air conditioner, the owner should ensure that the furnace or the air conditioner is less than ten years old.  If both of them have crossed the ten-year milestone, the heating repair company near me would suggest the owner replace both, which will save time, extra effort, and more money.  Although there is no problem replacing just the furnace, if owners notice that the other appliances like air conditioners, thermostats, ducts, or vents also need some professional attention, the repair or replacement should occur simultaneously.