I have a K model that is giving me a "actuator bd no echo" alarm. I replced the actuator board with a refurb from Fresenius. It tested well in the shop but apperared again during a treatment. Any suggestions?

This is a communication error between functional board and actuator board try replacing functional board.

Possible Actuator or Functional Bd problem. Can also be the deaeration motor (electrical noise). Check DeBug screen 13: If 2nd digit on the "IO" line is counting, could be motor noise. Poor Grounding can also cause this.

Newesttech,
Are you talking about screen 3 ,ACT1?
I don't have a screen 13.

I have also noticed that when I get the "no echo " alarm, my temp drops below 30.

Thanks for all your help, it was the funtional board.