I have a K machine, 1300 hrs, that has a bicarb pump that just stopped working in dialysis mode. It will work in rinse but not in dialysis mode. I've replaced the springs/seals and o-rings, done a rinse, then put it in dialysis mode to check the operation. It worked fine, passed test, but then when I put the hydraulics back in and double checked everything the same thing happened.

Any ideas? I'm thinking it might be the actuator board or cable.

Sounds like a ribbon cable being pinched. Check the ribbon cable from act. brd. to distribution brd. Also ensure the cover on the distribution brd. is not pinching the cable on the bic pump.

Check the bicarb wand reed switch connection and operation. Have cracked one when sliding the hydrolics back into the machine. Also, have had a piece of the wand magnet missing and would work (or not) depending on the wand placement.

I agree with atlanta Tech, I've seen that problem before and the reed switch was the solution. Pulled most of my hair out before I noticed in the debug screens that the acid pump was showing open instead of closed when plugged into the machine. Acid pump was my problem by the way but it works on the same principle.