There's a diagram in Greenberg's Repair and Operating Manual for Lionel Trains 1945-1969. It's on page 387, at least in my copy (which is an older version, but as far as I've been able to tell, the only thing that changes from one "edition" to the next is the cover photo).
This book is readily available on-line, eBay, in many hobby shops, etc. Almost everything in it consists of (reduced-size) reprints of Lionel service manual pages, but the 165 wiring diagram appears to have been specially drawn for the book.
I don't have a scanner, or I'd send or post a copy -- maybe someone else can do that.
Don
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