The AC of a Nissan Quest 94 is working fine but the controls in the back are not What could be the problem?

probably a bad ground somewhere in the system. Mine did the same thing so I traced out the circuit and ran a new ground. it works great , but now it can be turned on when the main system is off. Not like that is a bad thing, but before the main system had to be on before the back could be. it still shuts off when the key is turned off, and when the switch is set to off.