I was called to check out a drain the other day...this is a couter flow unit with the evap. coil sitting directly on the furnace...the owner tells me that for two years this set up has worked just fine but, now, the unit is leaking all over...I took the drain apart to check for any blockage and did not find anything, in fact the drain itself is dry...all of the condensate is making its way into the furnace and out the bottom....does anyone have any ideas on what the problem might be...thanks...Jason