Buderus GB142 - Strange Lock Out

mans442

Hello,
We have a unique situation with our client with an older Buderus GB142 with 24/30kW HX.
The customer is planning on upgrading to a newer system in January, but we are attempting to troubleshoot a Boiler Lock out situation on this unit.
The boiler shut down while in service mode after several 6A/6L codes.  
Initial troubleshooting included:

• Checking the 5A Fuse in the UBA3 unit ( version 3.6) - OK
• Unplugging the combustion air fan and Grundfros Recirc pump, still no power/startup.  LED display screen blank with no power.
• Checked for 120V into unit to the internal control board - OK
• Check for 120V power across the power control switch - OK
• Swapped out with known good spare UBA unit - No Change
• Swapped out 120V transformer with spare unit - No Change
• Swapped out with spare LED display power (white) control panel - No Change
• Swapped out with spare KIM switch - No Change

I am wondering if there is a safety lock out switch that was triggered during the service mode testing.  If there are any troubleshooting procedures on this topic, please let me know.

yellowdog

What's the sub code? Nothing you did will fix a 6a lockout. Get the service manual and go thru the ladder diagrams to find the issue. More than likely a bad inducer motor, sticky gas valve, weak ignitor or a bad flame rod.

Ironman

https://forum.heatinghelp.com/discussion/199429/buderus-gb142-strange-lock-out

Why are you doing these things to correct an ignition failure?