Curious DCC headlight

[Irbricksceo]

Hello, so, I clearly misunderstand how headlights work in DCC.

I finally got around to replacing the burned out headlight in my 2-8-0, put in an LED. Thing is, rather than being on constantly as all other DCC locos do, it goes off adn on brighter according to speed as if running on DC. the headlight function does disable/enable it but it has that scaling. Why would this happen? and yes, I've tried a decoder reset as I usually do when a decoder issue happens.

[thewizard]

My guess is that one of the LED wires is wired up to or otherwise making contact with the motor. The more power the motor gets, the brighter the LED is, but only if the LED is getting power from the function wire, too.

[Irbricksceo]

not a bad guess. I wonder.. If I wired the LED backwards, that could explain it. Due to the resistor and LED taking up space it is very possible the LED is comign into contact with a motor lead.

[Hunt]

After making sure the headlight leads are properly wired - If the installed decoder is a Bachmann factory installed sound decoder,  Program CV 49 to 129.

[Irbricksceo]

It is a standard (non sound) decoder. Either way, it is working now. Thanks though. I would not have thought LED backwards since it did turn on, did not occur to me that the motor lead could be making contact.