Lionel 18045 Chuff Sound

Top suspect would be the chuff switch activated by the main rod and cross head, which also activates the smoke piston. You’ll have to take it apart to inspect those components. Check the chuff switch for continuity from ground to the light blue wire when the switch is in the closed position. That wire goes from the chuff switch, all the way back through the tether, and into the sound boards. Chuff in is a separate line back in those days, it does not come across serial data like the whistle & bell do under command …

Pat

Yes, we can help. Very simply, you have a chuff switch system that has failed. That is why you only get the initial chuff from neutral to forward. To my knowledge, almost all Lionel steam TMCC engines of that era use a chuff switch and they do fail in some way (cam failure, switch failure, wiring failure).

First look up the product page for your engine at Lionel support https://www.lionelsupport.com/...-Hudson-C.-Venderblt

Specifically the engine shows the typical chuff switch actuated by the smoke lever and cam on the engine's axle.

Again, there are basically 3 known types of failure.

The chuff microswitch can fail internally and no longer toggle between normally open to normally closed. It breaks and is "stuck".

That switch is mounted in part 36

The cam can crack on the axle in many engines because it is a press fit over the shaft often splined or knurled and that cuts into the cam and causes a stress crack over time. Then the cam no longer grips the axle and you typically have to press the wheels off to replace the cam- however, there was a topic on a 2 piece 3D printed replacement cam in the forum. The symptom is rotating the wheels of the engine does not result in the smoke lever rising and falling and thus no puffing of the smoke unit either.

However, in this engine, it appears this is a lever driven smoke system driven by the crosshead guide? So in theory, no cam to fail.

Last, and probably most likely the problem is a broken pin or wire in the tether since specifically this is a keyed connector system using an extra pin on one side. The wiring from that chuff switch is one of the wires in this tether

Unfortunately that part is not available

FWIW, this post of a highly modified example of this engine also had the original wiring diagram- obviously edited but what I could find at the moment.

Mario aka @CentralFan1976 posted this here (also big thanks to @gunrunnerjohn who helped or may have been the co-developer or developer)

https://ogrforum.com/...60#73087246137602860

Again, my first guess is most likely a broken off pin missing from the tether. Just so happens, that is often the chuff switch one.

If it's not that, and the tether is functional, then the next likely candidate could be the switch, but check for mechanical operation first to ensure the lever system is puffing based on it being driven by the crosshead on one side of the engine. Again, if mechanically it checks out, this is a semi common switch failure.

Luckily, I think you don't have a smoke cam that could crack.

One more failure mode that's actually very common, simply a bent lever.  At least half of the issues I have with mechanical chuff switches are corrected by simply bending the lever a bit.

All the pins on the tether are there and the lever seems in place. I will look into the chuff switch then. Thanks for the help guys.

The chuff switch is far and away the most common issue with these older TMCC models.

Agree with John above, ….as we mentioned earlier n this thread, ….easiest method of diagnosing is to verify the chuff switch to ground ……..light blue wire is chuff …..verify this to ground ….using a DVM ( multimeter) set to continuity ( ring out) you can test the switch by rotating the motor shaft by hand and watching for a closed switch, this should ring it to ground ….and as John mentioned earlier, a bent puffer shaft can prevent the switch from fully closing and completing the circuit, ….to verify, when you see the switch is closed, use a pick tool or toothpick and try to close the switch further, …if it rings, try adjusting the lever for more contact on the switch,…..AMOF, my first test is to close the switch with a tool or toothpick, and see if the switch is truly dead, or just needs an adjustment……..clear as mud, ….right??…😁

Pat