Here's what it looks like:
BLI_Chuff_detail by Edmund, on Flickr
R=reed sw. M=magnet
The magnet is embedded into the brass flywheel. Glass reed switch on the bottom of the PC board. (some engines have a slightly different arrangement but basic concept is the same).
They are pretty fragile. I've broken a few inadvertantly. Lead in wires are stiff so they have to be supported before bending
BLI support is very good, in my experience.
Good Luck, Ed
It is almost certainly the sensor, or maybe the reed switch. BLI will offer to repair it if you contact them. These devices don't have a great life, and are prone to failure.
Maybe try the electronic chuff set by a CV, as already suggested.
When in doubt, best bet is usually to do a factory re-set and see if that works. It could be something as simple as you accidently changing a CV that set the volume of the 'chuff' sound to zero.
Ed,
I'm not certain but hopefully someone more expert will add some related info. Or you might e-mail tech support if you don't resolve this here.
https://www.broadway-limited.com/customerservice.aspx
I have a Paragon 2 which had a chuff sensor issue and they replaced it. I think it may be still a problem, last I checked. For that, the "Operators Manual" (pdf) indicates that the chuff can be set to operate without using the reed switch, by setting using CV233 & CV246. I'm going to try that.
For a Paragon (I have a Mountain) I presume that is a QSI decoder from looking. Which Operators Manual pdf to use I'm not sure. I don't know if those use a reed switch to sense the motor speed and vary the chuff rate. I see some CVs that can tweak the chuff to match wheel rotation but not anything about bypassing any reed switch control (if it has one).
The various Operator Manuals are here, which are much more detailed than the pamphlet that comes with the loco.
https://www.broadway-limited.com/supportdocumentation.aspx
BTW, have you tried a reset?
Paul
Modeling HO with a transition era UP bent
I lost the chuff sound on my Broadway Limited Paragone 464. All other sounds work fine, (bell, whistle, ect.) and it runs great. Could it be a decoder or wiper problem?