Nissan Repair: Heater controls, best guess, vaccuum

Question
I just got an 88 300ZX. The heater controls do not work. The blower motor works fine, but it is stuck on Defrost and I can't change the temperature, it only blows hot air. I tried a different control panel, but it does the same thing. Would this be electrical or vacuum. The car also has a slight miss at idle.

Answer
Hi Toby -

My best guess is that there is a broken vaccuum hose related to the heater control that opens and closes the duct door. While in the car (running) do you hear a slight hissing sound? If so, look for a disconnected hose or broken hose going to the heater door.

If not, the leak might be in the engine compartment. Check all hose runs for breakage.

Makes sense that if the hose is broken, you have a vaccuum leak, causing the rough idle.

Hope this helps -
aloha
calvin