My 83280zx2+2...has no heat when I put it to heat on the control panel..The blower works fine but no matter if the engine is hot or not the heat dosen't happen...The airconditioning also dosent work, would this be the reason??
Check under the dash and make sure that your heater control valve lever is
moving. If it is frozen closed, the heated water can't make it to the heater.
If your temp slide is difficult to move, the valve is probably frozen.
I had the same problem on my 75 which I got workin today.
Anyhoo, I fixed the vacuum leak which allowed the switching from defrost to heat etc.. I didn't have any heat though. So.. the slide cold-heat lever pushes a wire which in turn activates a swing arm control valve which is inline with the input heater hose from the core up.Apparently there is another wire connection from that swing arm that pulls in-out the inline valve which was missing. So I just took a pair of needle nose pliers and pulled out spiget on the valve. Its fixed temporarliy till I get a replacement connector.I doubt that the 75 is similar to your car but I would check the wire pushrod to the valve right near the heater core.