MY1999 996.1 • HVAC/Electrical • Exterior Air Blend Actuator -- Fresh Air Mode Noise

[tayloralexander]

Issue
There is a mild actuation noise emanating from the passenger bulkhead. The pitch and the speed of the sound ranges between fast and slow, sharp and dull as if it is going to stop yet continues again. More or less a pumping sound.

When the issue appears
When the vehicle is started; the HVAC controls default to Fresh Air Mode and whenever Recirculation Mode is disabled.

Present resolution
Enabling the Recirculation Mode on the HVAC controls will silence the noise.

When it first happened
The HVAC system and Actuator Motor were working without issue or noise. I purchased the 996.2 matte interior control buttons and had replaced them all with the exception of the HVAC control unit and the dome lighting module. I plugged in the 996.2 HVAC control unit... and turned on the vehicle; this is when the noise began. This event was a while ago; yet I remember that the 996.2 unit did not operate the HVAC as intended. So I immediately replaced the 996.2 unit with the 996.1 unit.

Questions I have
I usually live with Recirculation Mode enabled, and I have been occasionally researching the issue ever since and have yet to find any definitive answers to resolve or learn more about the system on the 996 Carrera. Hopefully this thread will assist others in the future.

1. Is it even possible to successfully replace a 996.1 HVAC unit with a 996.2 HVAC unit?
2. What happened in this scenario to cause this error? Was it preventable by way of another installation method?
3. Was the issue caused by a process or issue related to other electrical components such as the fuses or relays?
4. Do I need a new Actuator Motor for Air Temperature Flap and/or other parts {PelicanParts.com: Part No. 996-573-919-00-OEM}? Or is it possible to perform another function to correct or inspect and correct the present unit; i.e. inspect the cabin filter area or turn the gears within (I read that online in relation to other manufacturers)?
5. If I need to replace the Actuator Motor; does anyone know of a guide to follow?
6. Would this issue display on any diagnostic hardware/software?
   

Related Electrical Bonus Question
The other 996.1 interior component which remains is the glossy controls of the dome lighting module as the matte-finished 996.2 dome lighting module has a differing electrical connector. Is it possible to connect this with an adapter between the two without issue?

Thank you
Please advise what you would recommend. If you require additional information, I will attempt to reply with it. Thank you.


Porsche Actuator Motor for Air Temperature Mixing Flap, Part#996-573-919-00-OEM