On the left side of the sink vanity in the bottom storage area is a small 3" heat duct and very little warm air comes out of it when the furnace is running. Much less than the other ducts throughout the trailer anyway. Is this normal? Also behind the toilet is a floor duct that no air comes out of and I can see hot and cold Pex lines that run through there. Is that a cold air return for the furnace or is that a heating duct that isn't working and should be repaired? Thanks in advance for any input.