Dirty filters, blown fuses and failed thermostat batteries are among the top ten maintenance issues for gas furnaces. Problems with vent blockages and issues with the furnace's ignition system are also frequent causes of problems for gas furnaces.
Dirty exhaust filters are the primary maintenance problem for gas furnaces, with up to 90 percent of furnace problems due to this issue according to home repair providers Preferred Home Repair. A dirty filter prevents sufficient exhaust flow from the furnace, inducing shutdowns due to the furnace overheating. Electrical problems are also frequent culprits for a non-starting gas furnace, especially if the furnace is on its own electrical circuit.
Other issues among the top ten maintenance problems with gas furnaces include leaks in the ducts used to move air to and from the furnace, damage to the furnace's limit switch and clogging of the furnace's pilot light. Air leaks often cause odd squeaking noises from the furnace or ducts, but are often easily remedied with duct tape. Damaged limit switches are typically a result of a dirty filter that is not cleaned for a prolonged period, resulting in the furnace not shutting down even when the house is at a desired temperature until they are replaced. Clogged pilot lights prevent the furnace from igniting and need to be cleaned. Pilot light clogs are primarily an issue with older furnaces, as many modern unit use direct ignition systems.
Finally, issues with a gas furnace's blower motor are also among the top ten common repair issues for gas furnaces. The blower fan's vent can become clogged, leading to inadequate heating until the vent is cleaned. The blower motor may overheat under heavy use as well. Overheating issues are usually resolved by simply resetting the heater, but may indicate mechanical problems with the blower itself.