# No headlights after decoder install.



## starman151 (Jan 3, 2015)

Installed a MRC sound decoder in my new Atlas Silver GP40-2. Had headlights before decoder install but not after. Removed decoder and lights worked again. Any ideas??


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## DonR (Oct 18, 2012)

Are lights incandescent or LED?
If LED is the polarity correct from decoder?

What voltage comes from the light wires
of the decoder? Most supply 12 v dc.

Sometimes a re-read of the manual
will bring out a decoder setting that
controls the lights that may need
to be tweaked.

One of the MRC guys can likely point
you in the right direction.

Don


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## starman151 (Jan 3, 2015)

Lights are LED.


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## starman151 (Jan 3, 2015)

I am a novice at this so please forgive me. I thought when you used the 8 pin plug that the headlights were connected through the plug. Do they have to be wired separately??


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## Brakeman Jake (Mar 8, 2009)

If the lights work OK before the decoder then the eight pin plug is OK.

What's the decoder number?May be some programming can help.However,don't raise your hopes too high...MRC decoders are notorious failures.


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## Fire21 (Mar 9, 2014)

This may sound too easy, but when I installed my decoder, I had no headlight...until I read the Digitrax manual and saw that I needed to push a button to activate it!! (I am brand new to DCC.)


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## starman151 (Jan 3, 2015)

Thanks for the replies. It is a MRC 1711 universal EMD 645E. I use a Power Cab.


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## wvgca (Jan 21, 2013)

this may sound dumb, but did you push the f0 button ?? I 'assume' that this is not the only loco you have with dcc?? and are running on a dcc system??


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## Cycleops (Dec 6, 2014)

Could be that the headlights have been disabled by an incorrect CV value. As has been said MRC decoders don't have the best reputation!


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## starman151 (Jan 3, 2015)

reset the CV values and now have lights!!!!


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## DonR (Oct 18, 2012)

I learned something today.

On Digitrax decoders they list the LIGHT COMMON as the
blue Wire. I always assume, if there is nothing to the
contrary, that common is NEGATIVE. NOT with Digitrax.
Their decoder blue wire is POSITIVE, the yellow and white
wires for the rear and headlights are the negatives.

Could this be the reason your lights are not working
with the decoder in the circuit?

I had the LED light wires reversed. No lights, tho motor
ran well. After Digitrax quickly responded to my
problem (less than 15 min) I reversed the wires and
all was well.

If the lights are incandescent the polarity is of
no importance. My previous decoder install
used incandescents. 

Don


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## Brakeman Jake (Mar 8, 2009)

Digitrax aren't alone with a positive "common"...Soundtraxx does it too.May be it is a standard practice with decoders....


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## DonR (Oct 18, 2012)

If your lights are incandescent it doesn't matter, but
when you go to LEDs it does. Because they didn't
note 'common' as positive I hooked my LEDs up
backwards, and, of course, they didn't work.

They do make a + or - sign after the motor lead colors.

Don


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