ERROR 203 on MEIKO MODEL D 120.2

error 203 means , no change detected by the level switch when draining . possible cause
1, booster pump faulty
2, booster pump plug connector loose
3, start capacitor faulty
4, plug connector loose
5, boiler level switch faulty
6, no boost pump signal to- i/o pcb
7, no "boiler full" signal from i/o pcb check booster pump/ s2with manuel control

the most lightly or most common is the level switch in boiler tank will need changing