My air vent duct has developed 2 water spots, and one has opened up into a drip. I thought when I turned off the ac the moisture would disappear and I could fix the moisture damage. I was wrong, now that I have the heater on the leak is worse. what should I do?
not afraid of hard work
In the winter. The moisture is coming from heated air rising into the duct work in the attic. Cooling down, and then moisture condensing.
Put a piece of cardboard, or something to stop air flow in the winter.
This is guessing that your A/C is in the attic. And your heating system is in the basement.