Need HELP: SF Legacy Northern 6-11332 (3751) lost chuffing will only run 2 feet then stop

Sounds like its loosing its signal. What happens when you touch the handrails on the Locomotive?

CHRIS A, did it jerk on and off prior to stopping? is the whistle blow intermittently on its own?  

will it respond to cab-2 commands?

if all above is a yes then it might be like my first big boy issue and the RCMC board or the little board attached to it is bad. 

let us know 

OK here are the answers to the questions:  

I don't remember it jerking on/off prior to this problem starting up.  

The whistle does not blow "Intermittently"....   It will respond to all Cab-2 controls I gave it, even after it stops and the cab light is flashing...  I was able to activate the bell, the whistle, crew talk, open rear coupler etc.     It will even put on the reverse light in the tender, but once it stops, it won't move forward or backward....  and when it does move after a power down and power up cycle, it will move less than 18 inches, without any chuffing.   

J Daddy,  I checked the handrails, no change when I gently jiggle them.... It's definitely getting the CAB2 signal almost all other functions will work when programmed.

I wondering if I should remove the tender shell and make sure all the boards and plugs are seated in their sockets ??? any thoughts on the value of doing that ??

If the cab light is blinking continuously, that sounds like 1 blink to me meaning a motor, drive issue. Check that the traction tires are ok, the brake shoes are not interfering with the drivers.  

When blinking if you push the reset button on the cab 2 does the blinking light stop?  

https://ogrforum.com/t...-sante-fe-3751-toast

Sounds like the same thing that happened to mine.  Brace yourself for the worst on the smoke unit.

This models are just fantastic.....with some of the worst smoke units Lionel has used in the past decade or so.

FWIW, does your whistle steam still work when you quill the whistle?

This engine has a motor driver issue like Marty said. I had one Santa Fe northern 3751 that had a wire come out of its plug and do this .. Though I can't guarantee it's a loose wire. 

I'm with Marty, the Legacy units will run a few feet and stop if the encoder is not working properly.

Ok,  thanks to all for the input, feedback and ideas....  I will confirm that the blinking lights go out upon "reset"....  I am pretty sure they do..   Will also check for any mechanical binding, ie traction tires, brake castings etc.    

Failing encoder signal makes alot of sense as that's likely the signal driving the "chuffing"....    I assume the encoder is on the RCMC board assembly ?  Looks like the RCMC board is inside the locomotive, not the tender.   

As the suggestion from Alex M's thread on assigning a different engine # to try and unlock the RCMC is relatively painless I may try that as well.  

As I have both TMCC and Legacy on the layout, would this attempt to "unlock the RCMC", be more successful if I disonnect and power down the  Legacy base unit and do the engine # re-assigment with my Cab-1 and TMCC base unit ? 

The "encoder" is on the motor, under the toothed wheel.  There is a connector and wiring to the RCMC.  First thing to check is the wiring.

The RCMC is always in the locomotive, the link to the tender is just the IR signal through the wireless tether.

Thanks John.... I must have been having a senior moment there, obviously the encoder is reading and outputting shaft rotations (pulses) so it's not going to be on the RCMC board...

Cool...too bad it's the weenie gauge.

Well, it still could be the RCMC board, but the top suspect is usually the wiring between them or the encoder on the motor.

John, as always thanks for sharing your knowledge and experience.  I am doing alot of work on building a new module for the layout and wiring all the switches and block signals, so I probably won't add to the chaos and open up the northern till I get the other work closer to completion.  When I get around to opening up, I'll let you know if I make some progress.    

the blinking light does stop after a "0" reset, no mechanical binding, no tire issues, and it will move forward, or backward the same distance after a reset.   

Classic case of an encoder issue.  I have seen the exact same failure a few times.  With the older Legacy with the DCDS, it sometimes was the DCDS, the expensive part, and sometimes the encoder/wiring.  However the only ones I've had in newer Legacy with the RCMC have been the encoder or a broken wire.