Set Appliance State:
Set Multimeter to DC Volts 
Isolate Mains Power to appliance as per TOPs P4
DHW demand
DHW Selector in Maximum (+) position
CH Selector in Minimum (-) position
ON/OFF Switch in ON position
Drop the facia and remove the 6 screws from the PCB housing
Turn over housing to reveal the PCB
Use electrical insulating mat
DHW demand
DHW Selector in Maximum (+) position
CH Selector in Minimum (-) position
ON/OFF Switch in ON position
Drop the facia and remove the 6 screws from the PCB housing
Turn over housing to reveal the PCB
Use electrical insulating mat
| WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure |
Measurement:
Measure for DC volts on connections 3 and 4 on Plug X8, best contact can be made on the terminals direct on the PCB.
Expect approximately 5 V DC with DHW demand.
Notes:
Place the probes in the small holes on the PCB.
Ensure a good contact is made otherwise misdiagnosis will occur.
If in doubt repeat the test.
Expect approximately 5 V DC with DHW demand.
Notes:
Place the probes in the small holes on the PCB.
Ensure a good contact is made otherwise misdiagnosis will occur.
If in doubt repeat the test.
Isolate as per TOPs P4
and refit as necessary