That's how my 88 sami is.
My problem the fact that when i pulled the dash out i forgot to hook up all tubes that direct air to the vents, so i have some great floor head...and half defroster.
Maybe your hoses are off? Perhaps they got brittle and pretty much broke off, that's how one of my hoses coming from the heater up into the dash is...probably why i only have defrost on one side only.
I'm just to lazy to fix them

Well hope this helps out somewhat
Amilla