Nissan Repair: no heat, heater control valve, vacuum line

Question
I have a 90 300zx. My heater used to work just fine then one day stopped. It still blows air its just cold. The heater core does not leak. Could it be the blend air door? If so can I change it manually and where is it located?

Answer
Hi Brian -

A couple things need to be checked.

First, the heater control valve. Follow the heater hose, and near the firewall there should be an in line valve with a vacuum line attached to it. At this point you can check both the valve, and the vacuum supply to see if it is opening the valve.

If all that works fine, then the door is located in the ductwork under dash, passenger side. Sometimes it gets stuck and needs a coat of oil on the seals.

Hope this helps -
aloha
calvin