[Healeys] electrical problem

[healeymanjim]

no brake lights.  pressure switch checks OK.  wire from fuse box to switch good.  wire from switch to tab 5 on the relay box 
checks fine for continuity, but no voltage coming through.  knowing less about electricity than i should, anyone have a guess 
as to what is happening.  i thought the relay box might be bad, but with no volts coming through the wire it threw me off.  
signal lights work fine.  will try to isolate problem tomorrow.  any help appreciated.