Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to DC Volts 
Turn Hot Water Tap On
Gain access to PCB (use Insulation Mat as required)
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
Reset appliance if required
(press and hold the power button for 4 seconds then release)
Monitor the DC voltage across the blue wire on connector X21 and an earth (use the copper pipe to the gas valve as earth) during the ignition sequence.
Before the burner ignites approximately 0 Vdc will be present, as the burner is heard to ignite the voltage should change to
-10 to -35 Vdc (this is the rectification voltage)
Does the voltage behave as described?
(press and hold the power button for 4 seconds then release)
Monitor the DC voltage across the blue wire on connector X21 and an earth (use the copper pipe to the gas valve as earth) during the ignition sequence.
Before the burner ignites approximately 0 Vdc will be present, as the burner is heard to ignite the voltage should change to
-10 to -35 Vdc (this is the rectification voltage)
Does the voltage behave as described?
Isolate as per TOPs P4
and refit as necessary