Climate Control problem

Has any one had experience of the Ulysse Mk1 1997/8 climate control system failure.
The symptoms are no lights or display or display backlite on the ECU located below the radio and left of the gearbox. I have removed and dismantled the ECU which consists of two PCBs, one provides the display and switch control, the other contains the microprocessor and is connected to the vehicle wiring loom. I have checked with a meter and found 12V on the input connector regardless of the state of the ignition key switch. I would have expected a pick voltage to instruct the ECU to power up, therefore I don't know if the problem is the ECU or not.