Lionel 91 circuit breaker light not working

Sounds like you are on the right track to correct the problem (cleaning the points where the bulb contacts the metal parts inside the breaker).

Here is the Lionel Service Manual page on the #91 breaker.

Forgot to mention: There has to be a load in order for the light to go on.

Thank you C W. 

In reference to the load having to be there, do you just mean power to the track or do you mean an actual engine or lighted car drawing power from the track?

I think I have just answered my own question to the above along with your help CW which also is most likely the answer to my problem. I now think you mean that there has to be an engine drawing power from the rails. I discovered that my engine was not making good contact on the track and when I fixed that the light on the 91 when tripped makes the light come on.

Problem was solved once I cleaned the pickup rollers on my engine. Not only is my engine working better, but the light now lights brightly and steady on the 91 beaker when tripped. Who knew that was the cause of the problem.

Thanks again for your help C W.

Those 91 breakers are lightning fast and reliable. A shame they stopped making them.

-Roger