Took the relay out and the HDC fault went away immediately. At this point Im going to find another complete seat and go from there.

 

HDC faults are the first to come up when voltage is too low. I tend to think there is in fact a in issue with the seat, maybe motor that is stuck but trying to work. You would THINK it would blow a fuse though. But that is all I can think of. Maybe the previous owners gave up trying to figure it out also - hence the missing relay.