I have a Goodman H24F evaporator coil installed in the attic. It has both a primary drain pan, internal to the unit, and a secondary drain pan installed under the unit. The problem I have, for quite some time now, is that the secondary pan is constantly filling and draining through the secondary drain line. I am not sure what's causing the secondary pan's accumulation. I'd appreciate any help.
Some more information:
a. The primary drain line has been tested clean (water flows through it freely, it's not clogged).
b. The primary drain pan is brand new. It was replaced on the suspicion that the old one may have been cracked, but that prooved not to be the case.
c. The metal sheet underneath the primary pan is constantly wet. It is through this that the water drips to the secondary pan.
d. All internal side panels appear dry. Again the only wetness is on the bottom panel under the primary drain pan.
I am not sure how clean the coil is. The unit is 12 years old.