Troubleshooting Steps for Zone airflow issue

[JonC]

Hi,

I'm trying to troubleshoot an airflow issue of a 14 yr old house.
I have an NCM-300, 2 zones.
Zone 1 is upstairs. Zone 2 is downstairs.
My downstairs zone seems to have airflow fine.
My upstairs airflow has stopped. I checked the duct infront of the flapper, and it was closed, and seems to stay closed. The NCM shows both Zone 1 and 2 open (red LED), but I don't think I've ever seen the LEDs off, except for zone 3 which is not used.
I manually opened the closed flapped upstairs, but at some point, the system turned on and I the flapper was closed at some point.
I pulled the flapper actuator, and connected to zone 3 output at the NCM, and the little motor slowly moved.
I tested voltage for each zone output. Without motor attached, I see 28 volts. With motor attached, 5 volts.
I did find an issue with the NCM with possibly cold solder joints on zone 3 relay (opens and closes when lightly touched), but zone 1 and 2 don't seem to exhibit this behavior.
I'm trying to determine the next troubleshooting steps before buying a new actuator or a new controller board.
I'm suspecting actuator is the issue.
Are there any additional troubleshooting steps that I should perform before buying parts? Do the actuators need to be adjusted or orientated to reset its position?
I appreciate any suggestions or help. thanks

[Paul Z.]

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