I am not sure the exact cause of my headlight problem, however almost everyone who replied helped solve this mystery.
I took the hood off my engine, removed the bulb, only to find that the headlight is a unit that consists of a removeable lense, 2 tiny bulbs connecting 4-wires to a plug. if the bulb is burned out, the entire assembly (bulbs, wires & plug) must be ordered from MTH.
I disconnected the bulb and hooked it into the headlight connection on the other end. The light worked OK, so the bulb was not the problem.
Upon moving the bulb back to its proper place, the two copper springs that transmit power from the metal frame to the wiring connected to the plastic hood fell out. They don't stay in place without the plug holding them there, so when I unplugged the headlight, they fell out. Got very lucky and found them.
Finally got both front and rear lights working again.
What I learned about causes of a headlight not working:
1) if you remove the plastic hood for lubrication and maintenance, it must be put back on tight enough for the copper spring connectors to properly mate with the connector strips on the metal frame. If the screws that hold the cover onto the metal frame are even 1 rotation loose, the connection can be lost.
2) there are tiny wires near the copper spring connectors that can easily get caught between the copper spring connectors and the mating plate that brings power from the metal frame to the headlights in the plastic hood. if this happens, the light will not go on.
I believe #2 was my root cause, because the number boards on the front of the engine where also out. ( didn't notice that they were off, or remember that they should be lit up as well)
However, after I did my testing, troubleshooting and re-assembly, I created the case outlined in #1, where the screws holding the plastic hood onto the metal frame where not quite tight enough, resulting in a poor or incomplete connection between the copper springs and the connection plate on the metal frame. I discovered this by pressing down on the engine, while on the powered track, only to notice that if pressure is applied, the lights came on.
Learned a lot, gained some confidence in working "under the hood", got some exercise by going up and down the stairs 10 times (train room is on 2nd floor, workroom is in the basement) and ultimately got my engine working the way it should.
Thank you bluelinec4, gunrunnerjohn, AGHRMatt and Dale H very much for your help.
Joe K
