My headlight won't work

[Blind Bruce]

My loco runs fine. It reverse and respond to changes in CV etc. I cannot get my light to work. It is the original bulb that came with the Blue Box F7. I presume it to be 12Volts. I have it connected to the blue and white leads. The bulb has a resistance of 23 ohms and is in series with a 100 ohm resistor.
The system is Digitrax Zephyr and the manual states that the light should be controlles by F0.
Does the command station need to be in forward to enable F0? Anyhow, I think I have tried every possible combination and still no light. I chanhed decoders as well.
The Zephyr is new and I have not seen any functions work.but I doubt rhat it is faulty.
What else can I do????
BB

[MisterBeasley]

F0 means "function zero." On my Lenz controller, I simply press the "0" key to toggle the lights on and off. Of course, I have to be addressing that locomotive at the time, but if you can make it go, you're addressing it. Since you're connected to the white wire, the light will be on only when the locomotive is commanded to go forward, regardless of whether its speed is zero or non-zero. (If it's like my DH123D decoder, the yellow wire is for lights that are on in reverse.) Check your Zephyr's instruction manual to see how to control function outputs.

I'm assuming it's an incandescent bulb and not a LED. LED's are directional, and must be wired with the right polarity. From your resistor size, though, I assume you've got an incandescent bulb.

You might want to test the bulb by just connecting it, with the resistor, to the track or the accessory outputs of your power supply. If you have a meter, you can check the output across the blue and white wires - when it's on, you should get 14 volts or so DC, with the blue wire positive with respect the white.

FYI, I'm very new to DCC (like I bought it Tuesday) and I've already fried the forward light function output of one decoder. And I had to consult the manual 2 nights ago to figure out how to turn on and off the lights.

[Blind Bruce]

Yes, it is the bulb that came with the loco. There is no voltage between the blue and white wires even with track power on and the controller set to forward. I can push button zero till i'm blue in the face but no action.
BB

[rrinker]

If you have the control in forward, and give it a little juice, does the light come on then? Or continue as you were, use a voltmeter set on DC volts, plus lead tot he blue wire, negative lead to the white. You should get ~ 12V DC when the function is on.
Next question - what kind of decoder is it? Try resetting it to factory default. On Digitrax decoders this involves programming CV8 with the value 8, on others it varies. It could be that the function control CV's have odd values.
Do you have another decoder/loco to try to verify if the problem is in the Zephyr or in the the decoder? If another one works fine, the problem is the function is blown on that decoder.

--Randy

[Blind Bruce]

Randy,
I get only stray DC across the Blue and White leads. Very much like an open circuit. It does not vary when the F0 button is pushed.
I have one other loco (a B unit with no light) and that units decoder behaves much the same.
I will try to reset the decoders (TCS T1's)
BB

[rrinker]

I think that's setting CV30 to the value 30, but don't quote me, just from memory, I don't have a handy copy of the T1 instructions.
If there are blips, very likely it's set to some function effect rather than just plain light bulb. The output should show a steady DC voltage when F0 is on and no voltage when F0 is off. Check the yellow wire, too, F0R.

--Randy

[cacole]

Did you isolate the headlight bulb from the frame? The metal bracket that the light was originally mounted in is connected directly to the frame and is shorting out your decoder if you didn't insulate the bulb from the mounting bracket.

Did the bulb light before you put the decoder into the locomotive? Maybe the bulb is burned out, although it sounds like it isn't if you're getting a resistance reading through it.

[Blind Bruce]

Yes, the bulb is just hanging in mid air for testing. I clipped the leads and removed the assembly and placed the leads across the rails and the bulb lit.
I have yet to try resetting the decoders.
BB