Open gas valve power circuit. May involve high temperature switch, gas valve, or gas valve relay in control module.
1. Unplug connectoron supply sensor. Measure continuity of high limit sensor (close/open signal) between two pins connected to two purple wires. Is continuitly available?
Yes: -> 2
No: -> 3
2. Is wire harness connected to both gas valve and J13 connector on control module?
Yes: -> 4
No: Connect Harness
3. Is supply pipe ( coper pipe at top of boiler) hot?
Yes: Boiler has been dry fired. System has too much air. Close manual gas valve. Purge air from system, wait for system to cool.
No: Replace supply sensor.
4. Disconnect J13 connector on control module. Measure resistance across third (blue wire) and fourth (brown wire) terminals. Is resistance between 1.0 and 1.2KΩ?
Yes: Replace control module
No: -> 5
5. Disconnect harness from gas valve. Does each wire have continuity between gas valve and control module?
Yes: Replace gas valve
No: Replace Harness
