No heat
I know the temp dial works cuz if u put it on red with a/c on it gets warmer
I know the back defroster doesn't work rigt but thts a fuse problem ...and a common ls1 problem
you need to have the cooling system completely topped up with the overflow tank filled to the correct level. The heater core is one of the highest points in the cooling system so if air makes it's way there it tends to sit there, no hot coolant flows to the heater core and you get no heat. that will happen on almost any car.
You can also disconnect the 2 heater core hoses from where they come off the engine near the water pump, and blast fresh water via garden hose through the heater core to clear any crap out.



