Set Appliance State:
Set Multimeter to DC Volts 
Turn Hot Water Tap On
Isolate Mains Power to appliance as per TOPs P4
CH potentiometer set to minimum
Remove the programmer cover or programmer (if fitted)
CH potentiometer set to minimum
Remove the programmer cover or programmer (if fitted)
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
Allow fan to run and burner to ignite.
On the test pins behind plug ST16 measure the voltage across pins 15 & 16 (blue wires on connector).
Expect approximately 20 vdc or greater.
On the test pins behind plug ST16 measure the voltage across pins 15 & 16 (blue wires on connector).
Expect approximately 20 vdc or greater.
Isolate as per TOPs P4
and refit as necessary