Hi Dennis:
Just about everybody uses LEDs for headlights now. Keep in mind, it may not be the LED that has failed, but the output to the LED from the DCC board. If you want to troubleshoot this circuit, I'm sure I and others can give you simple checks to determine where the problem is. I gotta ask, since you are somewhat new to HO, did you check the easy stuff, like turn on and off the headlight with F0?
You have just stumbled across one of my pet peeves with HO; headlights. They can be a bear to install, and when they fail, we get to disassemble the shell to fix the darn thing. Since I'm not big on lighting my layout in general (my layout basks in permanent sunlight regardless of the hour 
), I don't get that hung up on headlights. I have an Intermountain F7 that I installed an ESU Lok-Sound decoder into that now has a failed headlight (3 mm LED). I don't know if it is the LED or the driver circuit, but when I have a choice of investing the time in taking off the darn shell, finding the problem, and doing what is needed to fix it, I'll live with the failed headlight until I don't have anything better to do with my time.
It gets worse with my brass steam, particularly articulateds. I HATE string wiring thru the boiler, draping the wiring down to the front pilot, drilling out the headlight casting, installing, finding a MV lens that fits and scrape the back coating off, put it all together, find the wiring interferes with front engine truck movement......................................................................
I'd rather invest my time in getting the drive to run smoothly, add as much weight as I can in the boiler and front engine (on articulateds), and making sure the sound is clear and synchronized.
Besides, I model 1952, and the requirement to have the headlight illuminated during daylight hours did not exist (not exactly sure when the requirement came in, and whether it was brought in under CFR 229, or earlier in CFR230) For that matter, neither did Rule 17.
Best of luck in resolving your problem.
Regards,
Jerry
