Editing Z31/hotairfromac php (section)

==== Defrost Vents are the only ones getting any air and it is hot ====

https://dev.z31library.com/xenonzcar_archive/2025siteimages/actuatorschematic1.png

This issue is becoming more common as these cars age past 40 years. The main causes are vacuum lines running to the actuators that have perished or cracked, or failure of the actuators themselves. The most common actuators to fail are the blend door actuator and the defrost actuator.

Unfortunately, these are also the most difficult to access, as they're mounted on the back of the heater box, buried deep in the dash. This means the entire dash and heater core need to be removed for replacement. From experience, the smaller actuator on the back (blend door actuator) is especially hard to source.

However, you can use aftermarket actuators as replacements with the help of 3D printing for brackets or adapters. Thanks to Nick Sturgis for developing a process that makes this possible.