Carrier APU problem

I have a carrier 6000 apu, the driver/ sleep control box has no power, wont light up. there is power going into the HVAC computer control board under the bunk but no power going out. I check all related fuses and connection hot and ground that I have traced. There is power to the APU starter and the hot wire from the ignition switch going to the APU is hot when ignition is on. I have replaced the relay under the HVAC control board, have replaced the HVAC control board and the driver/ sleeper control panel. Still no power to the driver/ sleep controls. Have anyone had anything like this happen and figured it out? I have a service and parts manual and have trouble shooted everything I could.

Skeeter