Everything on model trains, model railroads, model railways, locomotives, model train layouts, scenery, wiring, DCC and more. Enjoy the world's best hobby... model railroading!

Brand New! Just Released! 15 Background City Buildings To Download and Build

Decoder Light Problem

Warren posted this question:

“I fitted a decoder to my HO Bachmann loco and the lights don’t work. Is it a voltage issue?”

Add your comments below.

8 Responses to Decoder Light Problem

  • Allan says:

    Assuming that the lights worked properly before the decoder was installed, it sounds like the light function of the decoder is overloaded and may require a step down resistor in series with the bulbs being controlled. The bulb(s) may already have blown. You need to have a multimeter to check traces and make sure that the bulbs are not driven past their capacities.

  • Hervey says:

    Maybe a voltage issue. I am assuming you have a simple plug and play situation. What is the output voltage from the decoder? Is it running through a resistor?
    Also what type of lights are in the Bachmann. If they are LED’s and with no resistor between the decoder and the output from the decoder is nominal 12 volts then you probably fried the led. It happens so fast you probably wouldn’t see it.
    If the output voltage is running through a resistor and the Bachmann loco is equipped with incandescent bulbs you probably don’t have enough power to light the bulb.
    The paperwork for the loco and the decoder will tell you if the the voltage output is compatible with the requirements of the loco.
    Adding a resistor is fairly simple but if the led is fried you will have to replace it also. Neither of these jobs is terribly difficult just remember the polarity of the led is critical not so with the resistor.

  • Warren says:

    Lights worked before. I think I need a resistor as suggested above. THX.

  • Alvaro Sousa says:

    Good morning from Portugal Warren. As an official repair shop from Fleischmann/Roco, but also repairing other brands, first of all you don´t tell us what kind of decoder you are using, neither if the Bachmann loco is an older (split chassis) or a newer model or if it is a steam or diesel loco. As far as you say the lights worked well before you install the decoder, but are you using the same DCC system you used when you tested the decoder? If you are using another DCC system, see if this same DCC system is in 28 or 128 steps, because if it is in 14 steps, the lights don´t work. I you are using the same DCC system you tested the decoder, as Harvey and Allan says, see if the bulb is burned. If you changed for leds you also need to add a resistor in series, because if you don´t you destroy the led. The output between the blue wire (+) and the functions (white) front light and yellow (rear light) it´s about 12 volts. If you don´t made any error and no shorts occur, those lights must work without any problem. But please let us know what kind of decoder you are using and what kind of loco is. I hope this can give you any help. Regards.

  • Tony Oliveri says:

    Alvaro is right. I changed my DCC up from 14 steps then the lights came back on. I changed three Bachmann and one Walthers this way.

  • Tom Osterdock says:

    What brand decoder is it?

  • Timothy Purdy says:

    If you are doing your own programming you go to the lights tab. There it is preset to LED you have to physically change it from LED to LAMP by clicking on the arrow to the right of LED. Then make sure you go to the bottom and click “write page” or it will go back to LED when you exit.

  • Dan says:

    Take your loco to someone who knows decoder installation, otherwise, your are going to kill your decoder ! It is impossible to give you any advice here because many small things can go wrong

Leave a Reply

Your email address will not be published. Required fields are marked *

Add a photo or image related to your comment (JPEG only)


Use Tiny Railroad Micro Controllers

Download Your Free Catalog

N Scale Track Plans

Watch Video

Model Train Help Ebook

Model Train DCC HELP


FREE Tour Inside Club

Take a FREE tour inside the club.

Scenery Techniques Explained

Scenery & Layout Ideas

Model Railroading Blog Archive

Reader Poll

Sorry, there are no polls available at the moment.