Engine only runs backwards

[newtoN]

I am relatively new to model railroading and may have made a rookie mistake somewhere along the line before I placed my engine on the track.
Some detail may help someone provide me with what I hope is a very simple answer to my problem which is that regardless of which direction I place the engine onto the rails, it only runs backwards.
About 3 years ago I built an N scale layout with a total of about 27' of flexible rail.  I soldered 20-gauge feeder wires to the track at approximately 4-5' intervals.  I connected the feeder wires to a 12 gauge wire bus which I have connected to an MRC Tech 6 Sound Controller 2.0  All of the outer feeder wires are connected to one of the bus wires and all of the inner feeder wires are connected to the other.  There are 5 turnouts and 5 terminal ends included on the layout.  About 2 years ago, once I had all the track and wiring in place, I put my new Bachman diesel model 3274 on the track.  While the performance was not spectacular, I do not recall that it only ran backwards. 
For reasons I will not go into here I was unable to do any further work on my setup until this past December.  After a light cleaning of the track with a Bright Boy and minor housekeeping I once again wanted to see my train run before I ballasted the track and began any serious landscaping.  It was at this point that regardless of my best efforts I could not get the engine to run forward.  I have done some preliminary searching for an answer on the internet without success.  The closest I've come is several comments advising that there is a switch or wires on the engine motor that need to be reversed.  I hesitate to do something unnecessary and am reluctant to begin taking the engine apart if the problem is in the track wiring or somewhere else more easily accessible.  I live in a town that has no organized model railroading clubs or any stores with people knowledgeable about model railroad wiring or other aspects of the hobby so at the moment I'm at a loss for help nearby. I hope to locate some local help soon but would appreciate any help in the meantime.

[Maletrain]

I am not familiar with your particular locomotive, but, since you are not getting any other replies, I'll take a stab at helping.

I see that your MRC Tech 6 Sound Controller has direction control buttons and assume that you know how to use them.  So, I am going to focus on the locomotive, which I am not familiar with.  I suspect that it has a decoder installed in it to produce sounds, and that it might run on DCC as well as DC.  Please let us know if this is the case.

Also, please tell us what you mean by "only" and "backwards".  To try to be clear, let's say that you place the locomotive on your track with the "front" facing right, and when you turn up the voltage, it runs from right to left, that is, backwards.  When you try to change the direction by pushing the direction buttons on your controller, I am assuming that it still runs right-to-left, even though you tried both buttons.  And, the way I read your post, it seems that if you turn the locomotive around on the track so that it faces the opposite direction, it now runs left to right, that is still "backwards" with respect to what you consider to be the front of the locomotive.  

Is that all correct, or do I misunderstand something about what is happening?

[newtoN]

Thank you so much for taking a stab at solving my problem.  I was concerned that this was going to remain a mystery and I was either going to need to purchase a new engine or invest in a DCC only controller.  Here are answers to your questions:
The engine has a decoder but not for sound.
It will run on either DC or DCC.
If I place the engine on the track with the nose heading to the left, it only runs left to right, ie. backwards.
If I turn the engine 180 degrees and have the nose heading to the right, it only runs right to left, ie. backwards.
Regardless of the direction pressed on the controller, the engine runs backwards.

You did a good job translating my initial explanation.
I hope this provides you with enough to venture a guess at what I've missed.  I spoke with someone at Walther who runs N Scale and in the end he thought the controller may be sending a DCC signal but that the decoder might be translating it to DC somehow.  If this was the case then there might be a compatability issue. I hope a strictly DCC controller is not the problem. My budget would be squeezed if I need to spend $200+ on a controller and have the Tech 6 gather dust.

Thanks again for pitching in.

[Maletrain]

OK, with the clarifications, it seems that the DCC decoder in the locomotive is sending the motor the same polarity no matter what you intend.  That decoder is between the electric motor in the locomotive and the track, with a bridge rectifier between the track and the decoder.  So, no matter whether there is AC or DC on the track, and, if DC, no matter which rail is + and which is -, the decoder always sees the same DC power polarity as its input.  It needs to determine which wire from the decoder to the electric motor gets the + and which gets the minus, based on programming in the decoder and maybe programming in the MRC controller.  It is possible that the 2 are not completely compatible, or maybe one or the other is malfunctioning.

I really don't understand how the MRC Tech 6 is designed.  It would help to know what is really happening when you push the direction buttons on the controller.  Do you have a voltmeter?  (You really do need one to work in this hobby, but it can be a simple. cheap one - you don't need a special DCC meter, even when using DCC.)

If/when you have a voltmeter, measure the voltage across the rails as you increase the throttle.  In a normal DC controller, it should  go from zero volts to about 12 volts on the DC scale.  With it somewhere in the 10 to 12 volt range, push the direction buttons and see if the polarity on the rails changes.  For a regular DC controller, the rail that is + should become - and the rail that is - should become + to change the direction of a DC electric motor that is directly connected to the rails.  Knowing whether your controller is actually doing that will help us to figure out what is happening.  Most DC controllers use a simple dp/dt slide switch to change the rail polarity.  Because your controller has buttons and is designed to send some DCC sound signals to sound decoders, I am suspecting that those buttons might do things differently.

Another question is whether you bought the locomotive second hand.  If so, it is possible that the previous owner had changed a CV (configuration variable) in the decoder to not run on DC.  A lot of people who run DC/DCC capable decoders turn off the DC capability when they run them on DCC systems to prevent full speed runaways that sometimes happen when a decoder doesn't see a DCC signal soon enough after it gets power, so it assumes it is on a DC system, and, because it is really on a DCC system, it sees full track power and sends that to the electric motor.  Without the ability to use a DCC controller to read the appropriate CV in your particular decoder we are going to have a hard time figuring that out.

Have you joined the MRC discussion group on Groups.io?  That is the place that is most likely to be able to give you advice on what your controller is actually doing, and whether they have seen this problem before and know how to fix it.

[newtoN]

Thanks for the quick reply.
I purchased the engine (both A & B units) new from a hobby shop in Columbus, OH about 3 years ago.
I have a volt meter.  I haven't used it on the tracks yet but will use your directions to have a go at it.  I hope to get back to it shortly.  Right now all track is covered with tape because I've been using Sculptamold and plaster sheets to do some landscaping.  Can I uncover just a portion of the track to test it?

[Maletrain]

If you have enough uncovered track to see what direction the locomotive runs when you test the track with the voltmeter, that should be sufficient.  It is important to make sure that the voltage measurements are done in the condition where the unexplained loco behavior is really happening.

[newtoN]

So, the good news is that I believe the mystery has been partly solved.

I took your advice about checking the voltage across the rails and found no problems there either in the DC or the DCC mode.  Given that the voltage reading increased as I increased the throttle reading as it should, I then decided to try putting the engine back on the track.  With the controller in the DC mode the engine ran in both directions in the small portion of the track I uncovered (about 10") to do the voltage testing. With the controller in the DCC mode it only ran backwards. Apparently I had only tested the engine in the DCC mode since that was my goal for future operations. HOWEVER  I repeated the engine on the track test the next day and got the opposite results.  With the controller in the DCC mode the engine ran in both directions but only ran backwards in the DC mode.
At this point I'm happy that in one of the two modes it will run in both directions.  I only have one train running at the moment and it will be a while before I add another.
I'm thinking at this point it may be the decoder in the engine. Not sure what the next step should be short of replacing the decoder. 
Would temperature have any effect on operation?  My garage is in the low 40s until I turn the heat on and then it only gets into the low 50s.  I know that the temperature was about 40 for the last test I did.

[Maletrain]

I did HAPPEN to learn something about Bachmann BLUETOOTH decoders that may or may not be applicable to your situation.  For the Bluetooth decoders, Bachmann designed them to run with Bluetooth decoder control or DC, but not DCC on the rails.  To get THOSE decoders to run in DC when put on DC rails, Bachmann told me to increase the throttle (to about 11 o'clock on their DC throttle) and then CYCLE THE DIRECTION SWITCH BACK AND FORTH 4 TIMES to get the decoder to go into DCC mode.  Seems like a terrible PITA, but the only choice if the owner of a Bluetooth decoder equipped loco doesn't have a smart phone.  I don't know what happens when the throttle is turned down to stop after the Bluetooth decoder is in DC mode, because that seems to me like it would be the same as taking the train off the track, so MAYBE it stays in DC mode or MAYBE it reverts to DCC/Bluetooth mode and the throttle needs the 4x direction cycling again just to change directions.

Anyway, it occurs to me that something like that might have happened in your testing, if you cycled the direction control several times in DC mode.  And, I have no understanding of how an MRC Tech 6 throttle is switched from DC to DCC mode, either.  So, just another piece of info for you to think about as you try to figure out what is really going on with your combination.

I still think your best bet is to join the MRC discussion group on Goups.io to get better info.

[newtoN]

Thanks for the effort you've put in to helping me solve this mystery.
I'll take some time to digest and then try your recommendations and let you know the results.  In the meantime I'll carry on with my much needed work on the landscaping.  Time to get some ballast on the track for starters.