Gradually disappearing chuffs on Lionel TMCC Y6B

There’s a good chance it’s the wireless tether sensor between the engine and tender. There’s a way to check it but I can’t remember. You’ll have to wait for assistance or do a search. I replaced one on one of my engines having the same problem and it took care of it. 

I haven't worked on my 28085 Y6B of late, but I suspect being a TMCC engine, it likely generates the "chuff" input signal via a microswitch mounted near one of the front drivers-probably the "front" engine on this loco. Sounds like the microswitch has gone south.

I believe a digital camera will "see" the infrared signal if it's there and you can always tape the draw bar with painters masking tape to make sure the two pieces stay in line. Seems odd that the switch would fail only on corners, don't know how it is attached, maybe it's come loose?

Actually, it's pretty common for the chuff switch to fail only on curves, and even sometimes on curves in one direction.  My top suspect is the chuff switch.  If when the chuff is gone you can still blow the whistle, it's not the IR link, so you can stop looking there.

gunrunnerjohn posted:

Actually, it's pretty common for the chuff switch to fail only on curves, and even sometimes on curves in one direction.  My top suspect is the chuff switch.  If when the chuff is gone you can still blow the whistle, it's not the IR link, so you can stop looking there.

Is that the actual switch John or the wire part of it?

Both, though I've had numerous examples of the switch skipping on curves or straights and not on the other.  I attribute it to the slop in the axle moving the cam slightly.  Usually for those, I bend the arm a bit to correct it.  Obviously, if a wire breaks, time to solder it back on!

Returning to this thread, our chuffs on the Lionel TMCC Y6B completely disappeared.  But we can now see that wires have come off of a location above the second front drive wheel (see photo - white surface with 3 posts).  There is solder residue on the front 2 posts and back one is clean.

Does anyone know if this is in fact the chuff sensor, and if so, should the wires be attached to the front 2 posts.

Thank you!

The switch shown is certainly the chuff switch, and having all the wires missing is obviously a bad thing.

Solder them back on to the back two terminals, and it doesn't matter which wire goes to which terminal.

Thanks for confirming about the switch and terminals, John.  Seemed likely, but thought it good to check with the collective wisdom.

There's not a lot of room to work - wondering what's involved with separating the boiler.

It's not really hard to separate the front truck, but from that picture, I don't see the need.  Swivel it to the best side for access, and also allow it to droop as much as possible, and it should be fairly easy to reach in there with the iron and needle-nose pliers to tack the wires back on.