Buderus GB124 Condensing Boiler Problem - big time


Old 12-12-13, 05:01 PM
Thread Starter
Join Date: Dec 2013
Location: usa
Posts: 1
Received 0 Votes on 0 Posts
Buderus GB124 Condensing Boiler Problem - big time

I have a Buderus GB142 Condensing Boiler that quit last week and resulted in frozen pipes last Friday night. The local service person John, working with Buderus tech support, have been unable to diagnose the problem. I'm not the service person so I don't have the exact details but would appreciate any suggestions from anyone on the forum.

Last Friday during a cold snap, we found the system basically shutdown - the ignitor glows and there is evidence that the boiler is in a low fire state. After the initial startup, the relay on the control board starts buzzing. Pressing the "service" button, the unit initially showed a 2f 271 error code - that the temperature difference between the input and safety sensor was too high. We first hotwired the two primary circulation pumps with the boiler powered down and we are confident that they are spinning/pumping (how much is not known).

John checked resistance of the two sensors and apparently did not see a problem. After that check, a new set of error codes appeared suggesting a problem with the UBA (code u9). He checked the connections and reset the UBA in the base. No change

This past tuesday, the service person returned and called Buderus tech support. Buderus recommended replacing the low voltage harness ($340) as they decided that the low voltage connections were faulty. This includes the low voltage connectors to the UBA. Today John replaced the harness. no change. He then swapped out (from the neighbor's system) the UBA and the circuit/relay board, with no change though different codes seemed to appear though U9 is most common. We just checked the low voltage (somewhere on the unit, possibly by the relays) and it came back as 16v, though the check on Tuesday with the Buderus rep on the phone suggested that low voltage was ok. He then swapped out the 24v transformer and again no change.

So far, we have swapped out the low voltage harness, UBA, control/relay board, and the 24v transformer. U9 is the most common code - suggesting that the UBA is bad.

Any suggestions or questions I should ask the service rep? I should be able to get him to post responses to your questions (I hope).
Sponsored Links
Old 12-12-13, 05:36 PM
lawrosa's Avatar
Super Moderator
Join Date: Dec 2010
Location: Galivants Ferry SC USA
Posts: 17,964
Received 37 Votes on 32 Posts
Any suggestions or questions I should ask the service rep? I should be able to get him to post responses to your questions (I hope).
Not really... John has to follow the sevice chart here... If the UBA was changed and it still does not work it says to call the manufacturer...

Swapping the UBA from another unit is not a good idea unless identical parts.. IMO...

Did you have to buy the harness? The manufacturer should reimburse you if they told you to change that and it did not work... Your out $300 plus bucks...

This service manual is pretty detailed and is what I would follow if servicing your unit..

May I add this is why i dispise these high tech mod cons and IMO are more trouble then they are worth...

If you saved any mony on fuel with this unit its just going out the door now...!!!

Just saying is all... I know its frustrating...

Have one on me...


Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Thread Tools
Search this Thread
Ask a Question
Question Title:
Your question will be posted in: