I have a Trane central air unit. I have it for the 3rd winter now.

Water is dripping down to one of the air vent (not return) and leaking
to the floor. I have a HVAC technician took a look, but he said there
is no water in the Central air unit, and maybe cause by condensation,
however, I am not sure that's the case because even after we taped up
the return, the water is still dripping...

Have anyone experience this problem and know how to resolve this
problem?

Thanks.