My tailgate window has been intermitted going up for the past 8 years or so. Last year it finally gave up the ghost and stopped going up. So being stuck at home I finally decided to fix it. I bought a used relay controller box off of ebay for $44 and replaced it. What pain in the butt to access but I got it done. Now I just need to buy some clips for the overhead piece so I can finish putting it back together. For those who wish to do this, the part number is 85930-89105.

 

How did you diagnose the relay controller? I had intermittent issues with mine as well. I was able to disassemble the switch and file some fresh copper out of the contacts to get it working again.

 

I knew it wasn't the motor since it worked by putting power directly to it and the rear wiper was good and set. The window would work intermittently with both key and switch so it had to be the relay.