Musty odor after installing new furnace

I have a 10 year old house. The furnace died on us last March and we've just replaced it two weeks ago; we kept the old air conditioner and coils. I have been noticing that increasingly the air conditioner is now producing a musty and damp smell coming from the vents. It's been progressively getting worst every day and I can't determine the source of the problem. We've lived in the house for years and it always smelled fresh and dry and now after spending $4000 on a new furnace I find myself with this problem.
The person who installed the furnace said that he set the dehumidification to max by letting the AC start for a while before the fan would start.. so the coils would condense some moisture before the fan kicks in. The problem is that since the unit was installed, the house became very damp I've noticed wet paper towels stay wet for hours, unlike what we were used to before we put the new unit.
Can someone provide some insight into what's causing this?
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A couple of problems come to mind.
1) Check the drain to make sure it is draining properly, and not plugged.
2) The blower cfm on the new furnace could be higher then the old one. By slowing down the air over the coil, you gain better de-humidification.
Since the a/c wasn't changed, one of these two are more than likely the problem.
~kjpro~
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