Set Appliance State:
Set Multimeter to DC Volts 
Turn Hot Water Tap On
Isolate Mains Power to appliance as per TOPs P4
Gain access to PCB
Use insulation mat as required
DHW temperature control to MAX
Ensure boiler is cool so there is a demand for preheat
Gain access to PCB
Use insulation mat as required
DHW temperature control to MAX
Ensure boiler is cool so there is a demand for preheat
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
With the fan running measure DC voltage at the PCB test pin between the lower white wire at connector J4 on the PCB and a suitable earth point.
Expect approx 6.5V DC.
Expect approx 6.5V DC.
Isolate as per TOPs P4
and refit as necessary