Still trying to get smoke unit working on legacy 6-38415

By the way the smoke funnel was melted and one blade on fan impeller.

Here is the replacement parts page for your engine.  I didn't see a AC REG on it maybe you could find it.

https://www.lionelsupport.com/...84-ba73-040d100faaa6

Also for the smoke unit here is that page.

https://www.lionelsupport.com/...db-a07d-67e7752119e8

No regulator on that one, smoke units are controlled by the RCMC main board.   Also, on the RCMC board, no AUX1/x settings, just configuring the TMCC ID does the trick.  From the user's manual for your locomotive.

U-Boat (LEGACY) - 5/11 User's Manual

Hey, John tried it a few times in the past and I just tried it again nothing. On the board where the wires plug in. Right next to it is an open socket closer to the smoke unit maybe r7 if I remember right. Could I try and plug it into that one

By the way I'm using Legacy remote. I was reading and came across something about using aux-1 aux-2 to reset it. So I switch over the legacy remote to TMCC

I doubt that the moving the smoke connection to the aux smoke will work as that socket is likely not energized by the firmware loaded for the U-Boat, it doesn't have aux smoke.  J7 is the correct smoke unit connection.

The reset sequence is for TMCC, Legacy smoke control should work with the + & - keys on the remote.

Here's an excellent plug breakdown by Bruk Bannister, this illustrates where all the connections are.  Click on the graphic to expand it.  You'll see that J7 is the main smoke, that's the one that controls the smoke unit in this engine.

Thanks for your input LAZ1957 and GUNRUNNERJOHN. still nothing I'll have to tinker with it some more in a few day's.

Given that the smoke unit is a "dumb" unit in those, if the resistor measures around 8 ohms at the smoke unit connector and the smoke motor runs on 5VDC and pulls less than around 40ma, the smoke unit is not the problem.  If the board is the problem, there is no fix that I know of, short of replacement.