My defrost works in my 92 firebird but doesnt blow out the vent or floor heat.?

I took the contol box out and looked at it. There was 3 small plastic tubes on top of the heat a/c control or is connected to the actuator. I noticed that one of the holes wasn't open had something in it. I took the top of it off (the rubber piece that fits over the plastic tubes) and noticed when the rubber pieces fitting over the plastic tube that has something in it has a round hole also in the rubber fitting. Is this normal or is this the problem. Please help me figure out why I only get the defrost to work.