Your return valve and actuator is partially open to the spa return when in POOL mode.
You need to adjust the cam in the actuator to fully close the spa return when in POOL mode. Then
enable the Spillover function with dip switch #3 on the main panel. When switch #3 is on then AUX3 becomes the spillover control. If you have any relay connected to AUX3 you need to move it to an available Aux position.
With Spillover turned on by Aux3 the POOL/SPA return valve will move to the SPA position. Water will be suctioned by the pool and returned to the spa.
www.troublefreepool.com
www.troublefreepool.com