You could also connect an ohm meter to the bulb side of the connector, and take a resistance reading through the bulb. Then swap the leads on the connector pins and take another reading. If both readings are close to the same, there is no diode in the wiring from the connector to the bulb.
If your meter has a setting for testing diodes, use that setting for this testing.
Elmer.
The above is my opinion, from an active and experienced Model Railroader in N scale and HO since 1961.
(Modeling Freelance, Eastern US, HO scale, in 1962, with NCE DCC for locomotive control and a stand alone LocoNet for block detection and signals.) http://waynes-trains.com/ at home, and N scale at the Club.
Well, I did try both the F0 and the headlight button on my controller, and that didn't work. I suspect there might be a diode on the light. The wires (2) route through the loco superstructure between the shell and the lead weight, so I may have to remove it to see. The first thing I will do is to disconnect the wire connector that is just above the gear box. I disconnected it when taking the boiler shell off the drive and frame. It's possible that in reconnecting I switched the leads as the connectors did not seem to have a key that aligns wire polarity. It would seem that I could hook a voltmeter to the connector and check if it had power when the headlight function is supposed to be on. It probably won't be until this weekend that I am able to work on it. I think it is a bulb and will also try a 1.5 battery to see if the light illuminates. Just some random thoughts.
How about the obvious. Did you try turning it on (F0)?
Peter
Did the light have 2 wires running to it, or just one? And is there a diode in the circuit somewhere to make the light directional, so that it goes out when in reverse on DC? The one wire method will still work on DCC, it's called 'half wave' lighting. You just hook up the desired function wire to the wire side and leave the other side of the light grounded to the chassis. Uset he white wire for a headlight.
If there are two wires but there is a diode - you may have it wired backwards. The Blue wire ont he decoder is +. Either flip the wires or just bypass the diode, it's not needed in DCC for directional lighting, you can set the decoder up for that.
Lastly, is it a light bulb or LED? I'm guessing this isn;t a brand new loco fromt he past coupel of years and so probbaly it has a light bulb. But if it has an LED, and you didn;t install a resistor, you probably blew it out the very first time you turned it on. Unless you lucked out and wired it backwards. If it's an LED, again remember the blue wire from the decoder is the + side, and for typical DCC voltages you need a 1000 ohm (1K) resistor.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
This weekend I installed a Tsunami Hvy Stm 1000 in a brass HO Oriental 4-8-4. Everything went well and it is working fine except for one thing. He light won't work. I am 90% certain that it was working when I started. I will soon take it apart and check the light. Before I do that has anyone found a similar situation that perhaps programing or something would fix?