Don has earned a lifetime customer! My wife and I moved into our fixer-upper house this summer and just when the weather turned we realized that the 8 year old Goodman furnace in our basement had rusted heat exchange pipes and was leaking carbon monoxide. (So much for the $400 I paid to an home inspector before we moved in...) Fortunately, the furnace had a warranty still active. Not so fortunately, Goodman was incompetent in getting us the replacement part. It took them a month to send it, and then it wasn't even the right part. Don went to bat for us and convinced Goodman to foot the bill for an entirely new furnace! He and another worker made time in their busy schedule during thanksgiving week to come out and get the unit installed. This is above and beyond service and I couldn't be happier.
Natural gas furnaces operate similarly to the above, using a pilot light to ignite the burners and heat up the air. Also similar to propane gas, your average repair costs for a natural gas furnace will range anywhere from $125 for small repairs to $1,200 if you have to replace the entire heat exchanger. The difference between both options is not necessarily the actual furnace, but the type of gas used to burn through it and heat your home. As a result, the repair costs tend to be close to identical.
Your furnace's flame sensor is essentially a safety mechanism. As a thin metallic rod in front of the flame inside the unit, it's sole purpose is to confirm that your gas valves only open when a flame actually exists to burn that gas. When the flame sensor stop working, on the other hand, gas leaks can occur. To repair your furnace's flame sensor, expect to spend between $80 and $250. Even a full replacement of this part typically does not go above that range.
Cleaning the debris that builds up on your filters will aid with the flow of air. When your air filter is clogged, your air handler must work harder to compensate for the blockage of air flow. In addition to driving up your utility bill, the reduced air flow through your heating and cooling system can cause your heat exchanger to overheat and shut off too quickly.