If you’ve read gas furnace reviews on this site, you know that most furnaces come with a lifetime limited heat exchanger warranty. Heat exchangers are crafted.HomeAdvisor’s Air Conditioning Cost Guide lists price information on installing a new A C unit, as reported by HomeAdvisor customers..Thoughts on ” Cost to Replace a Furnace Motherboard Control Board ” Deborah Huffman . How does the board cost and the cost to have it replaced. My furnace is years old and its a ruud.The average cost for a HVAC Specialist is $. To hire a HVAC Specialist to complete your air conditioning project, you are likely to spend between $ and $ total..