Jim Banner.The reprogram did stop the runaway, but no luck on assigning a new address.The unit just keeps ignoring any new addresses and only stops if a reprogam is attempted.I guess we have to assume that the decoder has an address that overrides other commands.
I'm an old electronic engineer(now retired at 66 yrs) and took this as a nice learning experience and challenge with help from experts such as yourself.I understand how it could pick up an extraneous code the way you described and will now punt and buy a replacement Santa Fe for him.I really appreciate the help to date and look forward to more dialog with you and other model train hobbists.
Thanks again Jim.
Rako

Jim B and ABC As soon as I get to my grandson's I will try the reprogram again.I got confused before and tried to stop the engine first rather than see if the unit stops with the reprogram step Will let you know.

ABC-no dc on the tracks when I set the unit and off it went.
Rako

 ???To Jim Banner and others that offered help whenI asked about dc burning up dcc units,I now have a runaway machine.Now,instead of being dead on the tracks,it's a runaway!!!Before I could try to reprogram on the EZ command module,it started to run at full peed and at any and all 10 positions.Only way to stop it is to hit the stop button.
This is getting weird and humerous.Does this mean that the decoder logic is kaput and sending a signal to run,but why does the speed override the command module's rheostat?
Rako

 :)thanks for the reference.I figured out how to modify the broken holder(got a top piece of plastic and drilled a screw hole to retain the coupler.Works fine except the loco won't power up on the track.Worked fine before I put my hands on it.I'm an electronic engineer and know how to properly handle these kind of devices but don't  what happened.Are there sites that walk you thru troubleshooting?

thanks,I already picked up a few EZ couplers but now realize that the holder is either missing the top piece or damaged.If the four holes in the base remove the top assembly,is there a part I can replace or am I stuck?

Hi,I'm helping my 8yr old grandson repair his locomotives(commander set) and don't recall which type of coupler works best.Also,do you remove the entire housing on the loco or just fit a spring part back into it?

My grandson and I are new to model trains and could use some advice on replacing a broken coupler box for a bachmann Sant Fe GP-40(#3507)locomotive.
Do we need an exact replacement and where do we go to get one?I have browsed suppliers and am not sure what fits.
Dwight R