# programming mars light in MRC decoder



## KCSfan70 (Jul 1, 2017)

I have a PA with LED headlights. It has an MRC 1657 decoder according to MRC customer service when I sent him a picture. It has ed3530 stamped on the board. I have the white headlight wire connected to the bottom light and the yellow wire connected to the top light. I want the top light to be a mars light and the bottom light to be the headlight. It was like that before I had to reset the decoder because it quit working. I have tried many combinations in CV 117, 118, and 119. The manual MRC sent me says programming 2 into these cvs should give me a mars light. A different MRC manual says to program 8 into these cvs. I want to keep the decoder since it is one of the few decoders with ALCO prime mover sound. I mostly use Digitrax decoders which are easy to program with mars lights. Can anyone tell me how make the top light on this loco a mars light again? I use an MRC advanced squared controller. Thanks in advance


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## Cycleops (Dec 6, 2014)

Should be quite easy. Have you tried setting those CVs to 2 and then 8? One must work.


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## CTValleyRR (Jul 26, 2014)

Do you actually have a copy of the manual for that particular decoder? That's where the correct instructions should be.

The type of DCC system you are running doesn't make any difference (as long as it can program CV's of course).


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## KCSfan70 (Jul 1, 2017)

*mars light in mrc decoder*

1. I did not buy the decoder new and did not get a manual.
2. It was installed and programmed when I purchased the loco
3. I sent a picture of the decoder to MRC & he said it was a 1657
4. He sent a link to the manual which I printed
5. It said to enter 2 in CV 118/119 which I did with no change.
6. A different manual for 17XX series decoders said to enter 8 which I did with no change
7. There is nothing to indicated which wire goes to which cv ie: yellow, green, or purple.
8. I have connected each wire to the light one at a time with no change. 
9. I'm not sure what cv117 even does. 
10. All of this is very tedious & I'm ready to call it quits and buy a different decoder with The ALCO prime mover sound that I can actually program and put this decoder in a GP so that headlight and reverse light are all I have to worry about.-
11. Does anyone know if Digitrax makes a sound decoder with ALCO PA prime mover sound. 

PLEASE HELP!!!! Again thanks in advance


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## Cycleops (Dec 6, 2014)

Without seeing a picture of the installation it’s a bit difficult to comment further. Was it preinstalled from new by the manufacturer or put in later? Do the wires from the decoder lead to some sort of plug or do they just run straight to various wheel pick up / motor wires?
On re reading your post your best bet might be to follow the wires from the decoder. The blue is common so this will go to each light. The white is for the headlight. I imagine there is no rear light on the PA so the yellow is redundant. You will then need to identify the aux function wires to connect to your mars, the other will be common (blue). You will need a resistor wired into the circuit too if there is not one already. Your manual should indicate which CV operates the aux functions, that’s if your using LEDs, maybe you have bulbs?

Edit: it appears your decoder is a plug in type with an 8 pin connection. In which case your options are a bit limited if the relevant CV can’t operate the mars. Are you sure there is a bulb or LED in there and does it have wires leading to the light board or circuit board?


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## CTValleyRR (Jul 26, 2014)

KCSfan70 said:


> 1. I did not buy the decoder new and did not get a manual.
> 2. It was installed and programmed when I purchased the loco
> 3. I sent a picture of the decoder to MRC & he said it was a 1657
> 4. He sent a link to the manual which I printed
> ...


I understand your frustration, but please don't take it out on those of us who are trying to help you.

There are a couple of critical takeaways here, and you need to take a deep breath and make sure you are following what people are saying. Don't read too much into it.

First of all, you need to understand that each decoder out there has different capabilities and may require different instructions. You need the manual for the one you have, and no other manual. That's going to tell you what you need to do to program it. Apparently you have that manual. Get rid of all the others. They're only confusing the issue.

Secondly, you need to understand the limitations of BOTH the decoder and the locomotive it's wired into. The DECODER may support separate MARS light functionality, but the locomotive itself doesn't.

At this point, you have done so many changes to this loco, that who knows what may or may not be right. Do a factory reset on it, so you can start with a clean slate.

Next, make sure you are using a dedicated programming track. Sometimes, there is not enough current on the main track outputs to properly program a sound loco. In fact, early DCC units didn't envision the amperage requirements of sound decoders, and might need a booster to program properly. If you Advance Squared is more than 5 years old, adding a booster to the programming track might help.

Now, if Cycleops is right, and this loco only has an 8 pin plug on it, odds are pretty good that it doesn't support separate Mars light features, so to get them, you would have to remove the 8 pin harness and add a 9 or 16 pin one. assuming the decoder has an output that would support it. FWIW, the wires don't go to CV's directly, but to outputs on the board that the CV's control via the microprocessor. The wiring conventions are pretty standard, but it would be the loco's manual that would tell you what goes to what.

Now, all that said, while I'm a big fan of the MRC DCC Prodigy line, I'm not a big fan of their decoders, and ripping the existing one out and getting something different may be your best be IF you can rewire the loco.


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## KCSfan70 (Jul 1, 2017)

*Programming mars light in Marc decoder*

Thanks to everyone for the help. Link to manual from MRC was wrong. Tried programming info from 2 different manuals. Finally gave up, threw the MRC decoder away. Bought a Digitrax decoder with ALCO prime mover sound, plugged it in, programmed it in two minutes, headlight & mars light functioning. Happy ending. No more MRC decoders for me ever but love the Prodigy controller. Now I need to close this thread.


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