I haven't driven this car for about 6 weeks . The last time I drove it, I used the AC a little just to lubricate the compressor . The climate control seemed to be working normally at that time . Today, I drove it around and moved the temp knob to full heat . None of the fan buttons would turn on the fan . Nothing happened when I moved the knob to full AC ether . The fuses seem to be OK . Where do I start on troubleshooting this problem ? - Thanks

( 1990 300d W124 2.5)