Absolutely... the problem is that many times after clearing the
drain... it will become blocked again with a muddy type substance that
is the result of decomposing leaves and seeds that have made their way
throough the ventilation intake over the years. Actually, the one way I
have stopped the repeated clogging is to actually fill the plenum up
with water throught that same drain, in an attempt to rinse it out
good. The only other way is to take the plenum apart to clean as a last
resort.

Professor
www.telstar-electronics.com