s14 heating system

[lilskyline240]

i just hooked my heatercore back up after a long time of not having it connected...and i dont get any heat...the car warms up but no hot air?? i was reading somewhere that there is a check valve that the coolant flow only goes 1 way on teh s14 motor....is this true? also my coolant level is a bit low but that shouldnt make it not heat up??

any suggestions