That is "Stall Protection" basically Low Oil or Pump Time whatever you prefer to call it . I have replaced these before with octal base plug in timer. I think SP is normally always picked. When PM or UVR pull in to run up, it starts timer. If it takes too long then SP time expires opening the path to ground (HL1) at terminal 2 on SP timer. You may need a timer and a spare relay to accomplish this. Basically design your own circuit, I'm not sure there is direct replacement from Unitec.