I have a furnace that I haven't used in over 3 years, there is water leaking into my house from the vents in the ceiling, I am assuming it is some kind of condensation that has built up in the ducwork? Can I remove the ducts to stop this water? The vents in garage ceiling are really bad, we have checked attic and roof is brand new the water is coming from the heater vents.. help please!

No easy fix. You have to get up in the attic and trace it out,see where water is coming from and trace how it got there. It could be a condensation drainline loose or stopped up, might even be coming in around the exhast pipe/vent,, let us know what you find