Dashboard lights

I just had a new stereo installed in my 1995 Jeep Cherokee Country and I am now having 2 minor problems with the interior lights.
1) As soon as I start my car I hear the warning sound (annoying buzzing sound) for the lights being left on. My interior lights are on but very dim which never used to happen when the light switch was off. When I turn the headlights on the sound goes away. When I turn the headlights off the dashboard light dim and the noise starts agian. Any ideas as to whats wrong?

2) The lights for the Heater/AC don't work at all but the rest of the dashboard lights work fine. This is kind of stupid but I can't remember if the Heater/AC even had backlights to begin with. Does anyone know if the AC controlls are supposed to light up with the rest of the dash?

Many radios have a 'dimmer' wire which attaches to the dashboard light circuit. This controls the intensity of the backlighting on the radio and should be the only connection that the stereo has with the lighting system. This wire may be hooked up improperly.

Note, if the vent control backlight is out (yes the controls are backlit) this may be the source of the fault as the vent controls and radio are next to each other. Perhaps the radio installer incorrectly tapped the dimmer circuit power from the vent control backlighting.

Also, the new stereo may not have a proper ground circuit (the ground wire is not attached to the car chassis properly) or the ground wire was attached improperly.

Thanks for the info. I appreciate the response