Set Appliance State:
Mains Power Off
Set Multimeter to DC Volts 
CH Demand
ECO mode ON
Appliance in WINTER mode (no picture of a sun in the display,
press reset button to toggle picture of sun on and off)
Appliance in WINTER mode (no picture of a sun in the display,
press reset button to toggle picture of sun on and off)
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
Reset boiler as necessary and allow burner to ignite and establish.
Measure the DC voltage between pin 1 (black) and pins 3 (white) at the gas valve with the burner lit (voltage should be approximately 6V DC).
Put the appliance into summer mode (press the reset button once, a sun will appear in the display) while continuing to monitor the voltage.
As soon as the demand ends the voltage should return to approximately 0V DC.
Does the voltage behave as described above?
Note:
Negative voltage may be measured, this is ok as long as voltage is still approximately -6/0V DC.
Measure the DC voltage between pin 1 (black) and pins 3 (white) at the gas valve with the burner lit (voltage should be approximately 6V DC).
Put the appliance into summer mode (press the reset button once, a sun will appear in the display) while continuing to monitor the voltage.
As soon as the demand ends the voltage should return to approximately 0V DC.
Does the voltage behave as described above?
Note:
Negative voltage may be measured, this is ok as long as voltage is still approximately -6/0V DC.
Isolate as per TOPs P4
and refit as necessary