New answers tagged furnace
Colors of the wires is misleading, in reality there are but 2 sides or legs of 24 volt power, The "Hot leg" Red, and the "Neutral leg" Common. Common is called this because every 24 volt circuit terminates upon it to complete its circuit.
Common leg of the 24 volt control circuits is grounded, Red is not. Common is the side of 24 v power that every 24 v circuit terminates to complete its circuit.
A cracked heat exchanger comes to mind first, leaking supply ducts causing negative pressure, a bad thermocouple, bad
For the heat mode they are ok, for cooling I like the old horse hair reusable types we sprayed with sticky stuff, they filtered better as they got dirty and allowed air to flow for the AC mode.
Usually the evaporator coil is obstructed/dirty, this reduces the air flow. Pleated air filters that are dirty, closed registers, a broken heat ex-changer or a bad limit.
You need to install a return air grill designed to have an air filter installed. This is much more convenient and more likely to get changed as a result. The placement of a filter in the unit in an attic is not a wise choice.
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