I am having a problem with my central air. I get a odor coming from the vents when I turn the air conditioner or vent on. At first I thought it was a dead animal in the house or in my ducts, but its been months and the smell hasn't went away. It don't smell when the heat is on, only the air or fan. I can't understand why I would not have the same smell in the winter. We've checked the unit, there is no leaking water around it, we've took the cover off-nothing smells there, nothing smells at all in the attic (where the lines are running). Does anyone know what this could be? I don't know what I should do.

Check to see if the condensate drain from the foot of the AC coil is attached into a plumbing stack instead of draining to separate drain. It is possible to pull smells from the sewage lines.

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Yes, you really have to find out the MAKE and MODEL to get good answers. There IS more than one machine made.

I have same issues. Did you solve your problem. If so what did you do??