On further thought and some discussion if your unit is in an uninsulated attic you need to get up there and look for some leaks in the unit itself and any ductwork especially on the supply side up in the attic. for cold air to be coming in through that return duct you need to be losing hot air out the top somewhere.
This is what happened at my house. Ductwork in the attic had come apart.
01-30-2013, 10:59 AM
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