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