Set Appliance State:

Set Multimeter to DC Volts Set meter to measure DC Volts
Isolate Mains Power to appliance as per TOPs P4
Remove connector (blue wires) from modulating solenoid
Set service potentiometer to MAX
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Appliance On/Off control set to ON position.
Reset lockout as necessary.
Allow ignition sequence to commence.
After approximately 10 seconds measure voltage at disconnected connector.
Expect approximately 20 vdc or greater.