1 damper keeps opening an closing during heating cycle

[sbryant]

I have an ST-2D system with 2 zones. one zone and damper is working fine and one damper will open and close many times during a heating cycle. The furnace stays on to continue to hat the zone when the damper closes and a few seconds later the damper opens again. Occasionally the damper will work correctly and stay openfor the entire heating cycle. Do you think I have a bad damper? or a misadjusted motor arm? other thoughts?
Also where do I get replacements for the dampers if needed?

thanks
Scott

[Eric K.]

Does the motor you have have terminals 1, 2, 3, 4, 5, 6, Z & X? It is a Model MAN Motor Actuator.

Try disconnecting the #6 wire off of the motor, does the open/close cycling still occur? If so, it is a defective motor and would need to be replaced.

To locate a distributor, you can contact Customer Service and they can recommend a distributor in your area.

[sbryant]

nope. the motor on the damper only has 3 wires 1,2, and 4.

[Eric K.]

The motor you describe should only travel 180° then stop, if it continues to rotate, the switch circuit has failed and confirms that the motor is bad and needs replacing. If it has LED lights indicating open/close position, it is Model MA-SMDL, if no LEDs then it is replaced with a Model MRK.

Eric