8.10.2 Fault Finding - Bosch WORCESTER Greenstar Heatslave II External 12/18 Installation, Commissioning And Servicing Instructions

Last lockout memory feature
The control box allows the last lockout that happened to be displayed.
Access to this function is possible in both STANDBY and OPERATING
status.
▶ Keep the button pressed for 25 seconds = t < 30 seconds

8.10.2 Fault finding

Line
1 Control box is supplied with heat demand?
2 Is the pre-heater fitted or if no pre-heater is fitted, is the link fitted?
3 Motor starts after initialization check time 3.5 seconds?
3a Green 0.5 seconds ON/Red 0.5 seconds ON before lockout?
3b Fan motor or oil pump seized?
3c 230 Volts to motor across blue and black motor wires?
Approximately 35  across blue and black motor wires?
3d
4 Motor runs for less than 12 seconds?
4a Motor gives 50 Volts a.c. across black and white wires?
5 Burner does not fire, burner locks out after 25 seconds from motor start?
5a Burner fires when the photo cell is covered?
Photo cell voltage  3.8V in the dark and
5b
approximately 1.2V in the light?
6 Pump washing pressure 1 to 2 bar?
6a Pump pressure more than 6 bar?
6b Check oil supply to the pump, if oil supply is OK
6c Drive coupling broken?
7 Ignition spark present?
7a Are ignition leads and electrodes OK and set correctly?
8 Solenoid coil releases working pressure?
8a Does burner light or green 0.5 seconds ON/red 0.5 seconds ON
before lockout?
8b Contaminated fuel filters?
8c Coil lead OK
Solenoid coil resistance 90 to 110 
8d
8e After 15 seconds from motor start, 25 to 30 Volts d.c. to solenoid
coil? (coil connected)
Table 17
Greenstar Heatslave II External 2022+ - 6 721 843 980 (2022/01)
Check
▶ Release the button.
LED displaying the type of lockout memorised for 10 seconds
The time displaying the type of lockout can be extended by pressing the
reset button again during the display of the lockout (the lock out display
continues for another 10 seconds)
Yes Go to line 2
No Check boiler and system controls
Yes Go to line 3
No Fit the Pre-Heater or link
Yes Go to line 4
No Go to line 3a
Yes Go to line 5a
No Go to line 3b
Yes Replace seized component
No Go to line 3c
Yes Go to line 3d
No Replace control box
Yes Replace motor capacitor
No Replace fan motor and check control box
Yes Go to line 4a
No Go to line 5
Yes Replace control box
No Replace fan motor
Yes Go to line 5a
No Go to line 6
Yes Remove extraneous light
No Go to line 5b
Yes Replace the control board
No Replace the photo cell
Yes Go to line 7
No Go to line 6a
Yes Replace oil pump
No Go to line 6b
Go to line 6c
Yes Replace drive coupling
No Replace oil pump
Yes Go to line 8
No Go to line 7a
Yes Replace control box
No Replace/reset electrodes/ignition leads
Yes Go to line 9
No Go to line 8a
Yes Go to line 5a
No Go to line 8b
Yes Clean/Replace filters
No Go to line 8c
Yes Go to line 8d
No Replace solenoid coil lead
Yes Go to line 8e
No Replace solenoid coil
Yes Replace oil pump
No Replace control box
Fault finding and diagnosis
Action
55