Williams 1773512 Installation Instructions And Owner's Manual page 22

Point 13 (TR)
No inlet voltage (120 V).
Check 5 pole connector and control box.
If everything is okay, first replace the connector
and then the control box if problem remains.
No outlet voltage (24 V) during ignition.
Check wiring and connections.
If everything is okay, replace the transformer.
Point 14 (EV1)
Valve closed during ignition.
Check wiring, connections and voltage.
If everything is okay, replace the gas valve.
Point 15 (RP7)
No spark during ignition.
Check electrode, wiring and connections.
If everything is okay, replace the flame control box.
Point 16 (RP8)
No flame sensing.
Check flame sensor, wiring and connections.
...Check gas pressure and exhaust flue pipe.
If everything is okay, replace the flame control box.
Point 17 (EV2)
No voltage on EV2 with switch Z2 up.
Check wiring and connections.
If everything is okay, replace the switch.
Valve closed with voltage with Z2 up.
Check wiring, connections and voltage.
If everything is okay, replace the gas valve.
Starting Sequence (Gas)
1. Check and clean exhaust flue pipes;
2. Check and clean air blower and fan motor;
3. Check and clean burner and combustion chamber;
4. Check and clean gas nozzle;
5. Check gas type;
6. Check supply gas line pressure (see the manual);
7. Check gas losses;
8. Set burner gas pressure (see the manual).
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