No single speed 900w, every relay is labelled other than the blower there are two relays not labelled K14 & K12 the set up has 3 pumps 2 of those at high/low speed separate relays all labelled.
The board was made with a position K13 for a zettler relay bottom right of image labelled blower, but has solder filling the holes from manufactuer?
Originally the blower was intermittent stopping starting I tapped the board to try and find the relay and the blower stayed on and had to unplug.
I thought K2 was a possibility I tried to check with the multimeter but could not see the tracks to pick up the pins?!