A restricted filter is behind more heating and cooling faults than any other single cause. It makes a furnace overheat and shut down on its limit switch, it freezes an air conditioning evaporator coil into a block of ice, and it makes a blower motor draw high current until it fails early. The symptoms read as equipment failure even though the fix is upstream of the equipment.
Two details matter more than brand. First, fit: a filter loose in its slot lets air bypass it entirely, so dust reaches the coil regardless of the rating. Second, rating: a very high MERV filter in a system not designed for it restricts airflow enough to cause the same overheating it was meant to prevent. If a filter darkens within weeks, that points to duct leakage drawing in unfiltered air rather than a dirty house. Pro HVAC connects homeowners in East Fultonham, OH with HVAC professionals. Call (321) 463-9811.
