What exactly is clogged and how do I unclog it?
If it is clogged it would most likely be right at were the pvc comes out of the furnace.
Another possibility I don't want to think about is the A-coil pan has a hole or rusted through.
Have you ever worked with pvc or know someone who has?
You can first try snaking a wire up the pvc. It won't make it through the tee into the furnace but will check most of the pvc.
If it was me I would just cut the pvc then weld (glue) it back together with a coupler.