heater not workin

[daredevil302]

I have a 78 280z and when i turn on my heater it only blows cold air, and when i switch it over to defrost it still just blows out of the dash, not the defrost vents.If anyone knows what the problem might be, please let me know

[blackice280zx]

check your vacuum lines

[evildky]

first make sure the cables are actually attached and moving the things they are supposed to move, the heater control vavle ont hese IIRC is inside the firewall and controlled by cable, if allt he mechanical bits check out, you might simply have air in the system