DCC MRC auto reverse loop problem

Discussion in 'DCC & Electronics' started by nosweat, Dec 29, 2007.

  1. nosweat

    nosweat New Member

    I recently purchased an MRC Prodigy Wireless DCC system. I have been running one diesel locomotive (with a sound decoder) on the manline track without difficulty. The sound is incredible!

    Today I tried adding an MRC Auto reverse module AD520 to my layout. But when I plugged the Command Station into the power, the green pilot light on the Command Station failed to go on.

    I then disconnected the power, and disconnected the reverse module. I plugged the Command Station back on and the green light came on and I was able to run the locomotive. Placing the locomotive inside the reversing loop also worked fine. I then disconnected the power to the Command Station and reconnected the reverse module with the two red wires going to the mainline and the two yellow wires going to the track in the reverse section. But when I plugged the Command Station into the power, the green pilot light on the Command Station still failed to go on.

    I have two terminal tracks, one inside the reversing loop and the other on the mainline. I attached the two red wires to the terminals on the mainline track and the two yellow wires to the terminals on the reversing loop track.

    It seems that as soon as I connect the reverse module to the layout I am shorting out the entire system and the Command Station fails to turn on.

    I would appreciate any suggestion or comments.

    Seasons Greetings to All.
  2. Kevinkrey

    Kevinkrey Member

    I have a reverse loop and they all should be similar, but the wires should have one of each color going to each section. For example yellow to outer rail on mainline and yellow to outer rail on reverse loop. Red wires to inner rail on main and inner rail on reverse loop. What kind/brand of track do you have?​
  3. nosweat

    nosweat New Member

    You may be right ... but the instructions that came with the module say "Wiring - Connect the two yellow wires to the reverse loop section and the two red wires to the main lines section as shown."

    Before I try changing the wiring I would appreciate an indication from someone that I am not likely to damage the module if this doesn't work.

    I am using Atlas code 100 track
  4. Gary Pfeil

    Gary Pfeil Active Member

    The instructions are correct. Do you have both rails gapped at each end of the loop? If so I can not think of what may be wrong, other than possibly a defective reversing unit.
  5. Kevinkrey

    Kevinkrey Member

    Way to go Gary, Id put my money on that solution. I totally forgot about that. I laid more track yesterday and forgot to cut gaps causing a short. That is most likely the problem. I guess thats what they mean by two eyes are better then one, even though neither of us saw it.
  6. nosweat

    nosweat New Member

    Thank you for the comments.

    I definitely have both rails gapped at each end of the reversing loop. When I disconnect the Auto Reversing Module and then plug in the Control Station the pilot light on the Control Station lights up. I have power going to the mainline as well as the reversing loop track at a number of feeder locations. If there was a problem with the gaps, I should short out the system at this time, but it is fine. The loco moves fine on the mainline, and it also moves fine if I pick it up and set it down within the reversing loop. (All of this assumes the Module is disconnected from the layout.)

    I am beginning to lean more strongly toward a defective module.

    This is a great learning experience for me. I already have a much clearer idea of the logic underlying the wiring. My logic says the problem is the module.

    Someone on another Forum commented that I should not have power going into the reversing loop via feeder lines, but only through the red wires to the module and then through the yellow wires to the track in the reversing loop. I disconnected the feeder wires within the reversing loop and then re-attached the Auto Reversing Module. This time the Control Station pilot light lit up and the train moved fine along the mainline. However as soon as it entered the reversing loop it stopped cold and did not appear to be receiving any power. Does this help at all?

    I really appreciate the feedback thus far. I now strongly believe that I have the proper hookup (i.e. 2 red wires to the mainline, 2 yellow wires to the reversing loop.). I also believe that I have the reversing loop track properly gapped. I am not quite so sure about having the feeder lines within the reversing loop but that still makes sense to me as it needs a way of maintaining the power and signal throughout the loop. Therefore it is the module. or there is something else that I am failing to recognize or understand.

    I like a challenge, and this certainly is one.

    Thanks again to everyone who is trying to help. The Gauge is a great place with super people.
  7. Kevinkrey

    Kevinkrey Member

    Yea, might be a defective product. If you can move the loco from mainline to loop and it will work fine on each, I dont know what else the problem could be.
  8. steamhead

    steamhead Active Member

    Hi...the only power going to the return loop should be through the reverse module. The engine should operate going at least through one of the two legs of the loop. If it doesn't, you are not getting any juice to the reverse loop. Turn the system on and check with a voltmeter, light bulb (grain of wheat) or whatever else you might have to see if you've got juice in the reverse loop. If you dont, recheck your wiring...something's going on.
  9. nosweat

    nosweat New Member


    First, a very sincere thank you to everyone who has helped me with comments and suggestions.

    Steamhead's reinforcement of an earlier comment that the only power to the reversing loop should come through the MRC Auto Reverse Module helped. I then disconnected the two feeder lines that were supplying power to the loop.

    I now had confidence in both the attachment of the module as well as no extra feeder attachments to the reverse loop.

    I then turned the power on. The pilot light on the Control Station lit up indicating I had power on the mainline. I then tried shorting out the track on the mainline. This caused the pilot light to momentarily go off. Good. I then repeated this test on the connector track that had the two red wires going to the Auto Reverse Module with the same result. Good. I then tried it on the adjacent connector track that had the two yellow wires from the Auto Reverse Module but this time there was no short. The track was dead. Hmm. I tried this at a few other locations within the reversing loop with the same result. There was no current anywhere in the reversing loop. Hmm.

    The next step was the key one. I tried testing the two screws connecting the yellow wires to the connector track. The pilot light went off. There was power at the screws but not on the track. This meant the module was working fine, but the connector track was defective. I had just purchased this track so it was the last link in the chain that I would have thought would have been the problem.

    I replaced the connector track with another that I had lying around and everything worked fine. The locomotive entered and left the reversing loop without any difficulty. Yes! You should have heard the blast on the horn as the engineer indicated he was heading home.

    This has been an adventure, with a happy ending. I have learned a lot in the process.

    Best wishes to all in 2008.
  10. steamhead

    steamhead Active Member

    Good for you...!!!! Problem solving is one of the "arts" we have to master in this hobby. When we run into a problem we have to go about in a methodical, logical fashion to get to the cause, and then fix it. It's very frustrating at times, but the results are well worth the effort...:thumb:
  11. jud11

    jud11 New Member

    MRC Auto Reversing Module & Hello

    Hello to everyone at Zealot Forum,

    I just recently purchased a MRC Auto Reversing Module from e-hobbies and I must say so far it has worked great. I have a 28' X 11' layout that is all DCC. The system I use is a Digitrax Empire Builder II, I have 30 decoder equipped engines on the layout. I read some of the post before buying and was basically pleased with the options it provided. I recently added two reversing loops and one loop is partial integrated in the other. It took me about five minutes to figure out the insulating gaps and hook up the wiring but it worked great first time. There are a couple of trains that are headed up by three engines and they glide over the gaps as if there was no reversing loop characteristics there at all. Very satisfied so far, great unit great price now the only concern is durability.
  12. steamhead

    steamhead Active Member

    Hi Judd....Welcome to The Gauge..!! :thumb:

    That's some layout you have there. I'm sure it'll bring you many years of enjoyment (and some frustration...).
    I suggest you PM (private mail) to one of the moderators and ask them to move your thread to the "General Talk" (or HO Trains..if that's your scale) as you'll get more visibility since this thread is pretty much done with and won't attract much attention.

    Everyone would like to know you're here, and let us hear more from you..!!! :mrgreen:

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