Here is what I know   
The bulb is good. 
I have 12 volts on the R/Y side 
The RLU isnt pulling the ground down to light the bulb.   
Is this a common failure of the RLU?   
I found an interesting thread on removing/bypassing the RLU. That idea deserves some thought. 
When my starter switch needed cleaning, that particular device didn't tell me that my light was out anyway!