Athearn Challengers causing DCC to short when going over turnouts

Model Railroader Electronics and DCC
1

I’m having problems with both of my Athearn Challengers, UP 3983 and Rio Grande 3804 causing my DCC controler to go to short mode, it displays SVDA. The DDC is a MRC Prodigy Express. The 2 challengers are the older ones that came with the small hand remote when operating on DC.

I’m not super experienced with DCC, I was into model railroading as a child and teenager but this was 30-40 years ago. I’m now getting back into it and I bought a completed layout recently.

I’ve seen some turnouts for sale that are listed as “DCC Compatible”. Is that what I need? If so I’m guessing the turnouts on this layout are not?

I have other engines that work perfetly fine, a Broadway Limited 2-8-0, Broadway Limited SW7, and an Athearn Genisis GP7, they never cause this problem so it is something specific to the two Challenger Units.

Any suggestions you would have would be appreciated as my 8 yeaer old really wants to run the Challengers!

2

I presume “over turnouts” means through the diverging (curved) portion of the turnout? Also, what size turnouts are these issues happening on?

Given those are really large locomotives, I’m going to guess that the front pilot wheels are shorting to the chassis. You can verify this by removing one of the them and running that locomotive through the turnout.

Tom

3

Thanks for the reply.

This happens when going straight through the turnout or when taking the diverging route.

I don’t know the size of the turnouts, how do I measure that?

Taking the pilot of sounds easy enough, next chance I get I will give that a try!

4

I had a problem like this with Peco turnouts. The frog itself on these is plastic, but the approaching rails almost touch at the frog. So, engines with wide wheels would sometimes bridge the gap between the metal rails and cause a short.

Believe it or not, the solution was to put a dab of nail polish on the frog gap, insulating the the rails by effectively making the plastic section a bit larger.

I’d recommend either black or clear polish, to make the fiix less noticeable.

5

I forgot to mention that I’ve tried this already with little to no improvement, but perhapds I didn’t do a good enough job? I could always try again.

6

Doggone it, Mr. B. beat me to it.

Since the other locos have no problem traversing the turnouts, its gotta be the Challengers. The wider driver wheels touch converging rails of opposite polarity on the turnout causing a short. Clear nail polish is your friend.

Rich

7

Check your wheel gauging. DCC systems react to the slightest indication of a short circuit, and out of gauge wheels are one cause.

Basically, almost all turnouts are compatible with DCC. Some may require a few tweaks to eliminate issues.

DCC Friendly Turnouts

8

If the wheels are out of gauge can that be corrected?

9

If the two Challengers don’t derail on the rest of your track including curves, I would just concentrate on the turnouts. Try more clear nail polish. At one time, I used tiny slices of masking tape at the points of rail convergence.

Rich

10

It can be done. It may be a simple thing, but with a steam locomotive’s mechanism, it is best to get help from someone who knows what to do and has the tools. It is too easy to make a mistake and introduce a new problem, especially with respect to the quartering.

Also check the turnouts with the gauge to ensure everything there is correct.

11

FWIW I have an early Athearn Genesis blue box Challenger, model G9123 D&RGW #3802, that traverses my entire layout with no problems. This includes almost 100 turnout

12

Probably better for you to check the gauge first rather than get your drawers in a bunch unnecessarily.

13

I tried running it without the front pilot and that made no difference. I’ve ordered a track gauge and I’ll do some checking once I get it.

I’ve heard the MRC decoders in these aren’t that good. Is it possible the decoder is causing this problem?

14

I’m still thinking that it is the driver wheels touching converging rails of opposite polarity.

Rich

15

Track gauge arrived and I had a few mintues to check each locomotive, all of the wheels fit within the gauge, a few were tight but this was because they were just a bit on the narrow side, not too wide. However I had no problems getting the flange of each wheel pair into the gauge.

One thing however that I didn’t think about earlier is that the rear drivers are missing the traction tires, they were dried out and falling apart so I just removed them. The gap left without the traction tires is wide enough that a rail will fit inside it. I wonder if that could be the cause of my problems??? I’d like to replace these but it does not look trivial and I don’t have the easiest time working on small stuff like this.

I haven’t had time yet to check the gauge of all of the turnouts yet.

16

I would be real surprised if the turnout rails are out of gauge. The more likely reason is that the wheels are touching rails of opposite polarity.

Rich

17

[quote user=“CharlieM”]

After replacing the original MRC decoder with a Tsunami 2 it’s a reliable and well performing engine. I would look

18

So who made the turnouts and what model are they? The fix for Pecos is easy and obvious. If they’re not Pecos, we need to look further.

19

Anyone have an opinion?

20

Easiest way is, when you bought the turnouts, the package would say something like “No. 4 turnout” or “No. 6 turnout”. The higher the number, the more gradual the angle of the turnout. If you don’t still have the packaging, it may have information on the bottom of the turnout. If nothing else, might have the manufacturer name and a part number you could then use to look up the turnout online.

I suppose it’s possible the missing traction tire could cause a problem, though it seems unlikely to me. If you can get another one from Athearn, undoing one siderod connection to slip it on isn’t all that hard. Otherwise you could try filling it in with Bullfrog Snot and see if that works.