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Errors


Boiler type UBSSC-050

Error code A05

Cause:

Open gas valve power circuit. May involve high temperature switch, gas valve, or gas valve relay in control module.

Solution:

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