Have HVAC Questions? Ask an HVAC Expert for Answers
If you can send me a few clear photo's of the condensate drain lines as the exit the drain pan, that also show me about 5 feet around in all directions (photos taken from 8 feet away will work).
I can evaluate the situation for you.
So far it sounds like the primary drain outlet is clogged inside the drain pan as you suspect... you will have to remove the 20 x 20" panel on the coil cabinet to access the drain pan and inspect that.
We are on the honor system here. Please remember to rate my service before you leave today, the company only pays me if you rate my work. It is how I earn a living, and does not increase your charges.
If you need anything else, just let me know. You can continue asking follow-up questions at no additional cost.