Set Appliance State:
Set Multimeter to AC Voltage 
Turn Hot Water Tap On
Isolate Mains Power to appliance as per TOPs P4
Attach U-gauge to burner pressure test point
CH/HW switch in HW position
On/Off switch to ON
Ensure connections on base of PCB27 do NOT come
into contact with boiler during test, as shorting will occur
Attach U-gauge to burner pressure test point
CH/HW switch in HW position
On/Off switch to ON
Ensure connections on base of PCB27 do NOT come
into contact with boiler during test, as shorting will occur
| WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure |
Measurement:
Burner pressure should be at maximum setting.
Adjust DHW flow rate to the minimum required to keep boiler firing.
When DHW reaches approximately 70 deg C, check voltage across the plug-on connector
marked CON 2 GAS VALVE 3 (violet) wires on PCB 27, and the burner pressure on the U-gauge.
Notes:
This test is specific to the failure mode that you have selected - 'Hot Water Too Hot'. Please pay particular attention to the 'Pass' and 'Fail' criteria.
When U-gauge is removed pressure test point should be tightened & checked for gas soundness.
Adjust DHW flow rate to the minimum required to keep boiler firing.
When DHW reaches approximately 70 deg C, check voltage across the plug-on connector
marked CON 2 GAS VALVE 3 (violet) wires on PCB 27, and the burner pressure on the U-gauge.
Notes:
This test is specific to the failure mode that you have selected - 'Hot Water Too Hot'. Please pay particular attention to the 'Pass' and 'Fail' criteria.
When U-gauge is removed pressure test point should be tightened & checked for gas soundness.
Isolate as per TOPs P4
and refit as necessary