2001 megane hatchback heater control

Hi I just wondered if someone could help.I replaced 2 bulbs that had gone behind the heater controls and at first all was fine then they went out. I messed some more and after a bit of flickering they stopped working at all. The problem now is as soon as I plug the electrical connector back into the heater control unit all the speedo dials etc and the radio display lights go really dim but if I unplug it they go back to normal and really bright, everything works normally just not the illumination of the controls/dash