The single most common problem with residential furnaces is a dirty, clogged air filter. When homeowners neglect regular filter replacements, dust, pet dander, and debris accumulate rapidly, severely restricting airflow through the furnace cabinet. Restricted airflow forces the heat exchanger to overheat, triggering high-limit safety switches that shut the burners down to prevent a fire hazard, resulting in the furnace blowing cold air or failing to heat. Other common issues include faulty igniters, dirty flame sensors, and failing blower motor capacitors.
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