Oh my god!

It's that guy (apparently the newbie from hell) with the '81 Westy again, and 
this time he wants to know if anyone has any ideas about how to fix his horn and 
backup lights.  The fuse is good, but the horn itself is not.  The lights are 
good, but they don't shine...like there is some weird secret behind the design 
of the whole thing.  Is the horn button supposed to have only 90% resistance?  
Could that be one of the reasons that the thing was unplugged?  Exactly what 
relationship (besides being on the same fuse) do the horn and backup lights 
have?  If one is defunct, does that make the other so?  Where, pray tell, is the 
switch for the backup lights?  It looks like all the wiring is in good order, so 
I'm hoping for simple stupidity on my part.....

Thanks again, 
Gene ('81 Westy named Edward)