My cab forward (DCC Decoder installed) has lost the “chuffing” sound while all other sounds work…water pump, steam let off, bell, whistle, etc. This happened once before and I unplugged and re-plugged the tender plug and solved the problem but now nothing changes.
A member of our club had to send one back to BLI to have the tender wiring straightened out. It seems that it was either mis-wired at the factory or when it was sent to BLI for a previous repair.
There was a similar question asked about an engine like yours back in June of 2010. In the three pages of the topic the need to replace the chuff sensor was discussed. I think in that particular case it was found that a plug from the chuff sensor to a PCB connection had worked loose. Also in that post are some instructions on how to get the boiler off to access the sensor. I’m not sure which loco the instructions apply to since there were two locos with the same problem.
Also, there is another website where someone had a problem with a Broadway Y6b chuff sensor. A description on how to get that unit apart and some pictures of that loco’s internals are included.
I’m sure if you Google your question you will find these sites.