A/C and brake light problem

[Gilbert]

Hi, I have a 940 1992 , all the lights in the back work with the exeption of the 2 brake lights that are installed in the trunk lid. Each side has 3 bulbs at the end of the fender (position , brake and turn) and 3 more in the trunk lid: position, reverse and brake I supose, the 2 brakes aren't working
every time I press the brakes I get the fault light on in the dash.

The other problem is the AC: it works always, if I try to get heat it blows cold (and I can see the compressor engaging, if I push the Ac off button , the same, the fan speed selector works and the selector switch that controls where to blow the air works also, but it seems that the temp control does not work along with the ac off. I took the unit out and somebody had connected an external relay.
Any suggestions?