1995 Bounder Ford Chassis Monitor Power

Back trying to get our back camera working, seems the monitor has power and a white screen now, but no power at the plug at the camera mount. I am thinking we have a problem with the relay/solenoid that supplies power to both the camera and monitor. This is located in the Battery Control Center as Richard told me some time ago. When we cycle the switches for the aux and main batteries shut offs the main one does not always cycle. Questions, how do I trouble shoot the relays, do I just replace or get a new camera and monitor?? 2 wires going into the camera, I am assuming one is power 12V and the other is the picture back to the monitor. I saw somewhere that the power for the camera comes from the monitor. Confused where to start, don't want to purchase new unless necessary. Thanks for help.