Out of my ac ducts I get black soot that appears on walls &windows.
I had my vents cleaned 5 yrs. Ago & they seem clean.Please help.

Does the A/C unit also have a furnace connected to the same duct?

Does the A/C unit also have a furnace connected to the same duct?

It's a combination air conditioning/ elecrtic heat pump
Last year I noticed white dust on furnature but now it's like a black soot that is on the windows & walls & seens to be getting worst. I change my filters regularly.
Thanks

If it is a electric unit then there is no problem with a cracked heat exchanger. Are you sure it is from the HVAC equipment? If it is I have NO idea where it is from since the type of unit you have does not cause this type of problem usually. Do you burn candles? Things like that can cause this problem.