I have a Nissan 300zx Z31 and i cannot get the heater to work. When I turn on the heat only the defrost will come on. None of the vents except those will blow out air. I do not know what to do andi need some help.

 

Check the vacuum lines.

 

Checked all the vaccum lines and still no hot air. I also checked the water **** and it is down. The sv/8 does not have power to it though. Also when i hit the demist or the defrost button my a/c will automaticly turn on

 

You're A/C is supposed to turn on when you put your demist/defrost on. The A/C draws out the moisture in the car, so its not blowing humid, hot air at the windshield.