View Full Version : dcc directional prob
06-05-2007, 07:40 PM
I am brand spanking new to DCC and I installd my first decoder. The engine and lights worked fine but when the throttle was set to forward the engine would actually move in reverse and visa versa. The lighting direction was correct but the engine moved in the opposite direction. It did this in 3 differant locos that I tried. Why?
06-05-2007, 08:13 PM
Welcome to DCC!
What decoder were you trying to install? If it was one with an NMRA plug on the end, you have it plugged in backwards. Unplug the decoder and rotate the plug 180 degrees and plug it back in.
If it was a hard wired decoder, try reversing the wires to the motor.
Hope this helps!
06-05-2007, 08:20 PM
It is an MRC model #1638. It is a plug and play decoder. I tried reversing it but when I did that the lighting did not work at all. However, when I reversed it the engine moved in the proiper direction. Iassumed that since the lighting did not work it must go in the other direction. What do you suggest if the lighting is not working at all?
06-06-2007, 06:36 AM
look up the directional value in the cv that's the problem there. I forget what number that is someone else I'm sure will chime in, but change the value and youl'll be fine.
06-06-2007, 06:54 AM
I've run into this exact issue a few times already. I simply reverse the wires to the motor and wah-lah...problem solved!
06-06-2007, 06:59 AM
It's a plug though that is setup specifically for certain other wires to go to certain lights, he tried reversing the plug which fixed the direction but caused the lights to be wrong. That's why I said just program a different value to the direction variable.
06-06-2007, 07:28 AM
What Nick said. There is a CV, CV 29 that will allow you to reverse the direction of travel. IF it is not listed in your instructions. Got to the MRC website and download the manual. It is not a problem, it's a feature.
06-06-2007, 02:25 PM
I had some trouble programming cv29 with a four digit address but I managed to change the direction with the factory default address of #3. (Im still learning how to do it) When I programmed the cv29 the direction of both the lights and the engine changed. Right now the engine moves in the correct direction but the lights are reversed. i am attempting to figure out the CV that changes the light direction now.
06-06-2007, 05:29 PM
Does anyone know the CV that I would use to change the direction of the lights only for an MRC #1638 decoder?
06-06-2007, 06:16 PM
See if this is any help:
06-09-2007, 11:31 PM
Problem solved. After reversing the polarity I to get the loco to run in the correct direction, I reversed the wires to the lights. Now the directional lighting is corrected along with the loco direction. Thanks for the help.
06-15-2007, 03:01 AM
cv 120 controls forward light, default is 1
cv 121 controls reverse light, default is 2
to switch lighting just change cv 120 to 2 and cv 121 to 1, done same thing myself many times, also to change engine travel I change cv 29to 39
works for me
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