heat/cool selector stays on hot

Try driving in 80 degree weather with the heater on. I have replaced the compressor, drier and expansion valve.

Update from Jun 3, 2015: I had to buy a used heater box for a part that I couldn't order. The control arm on the bottom of the heater box kept falling out. Turns out it had two broken plastic tabs. Volkswagon wouldn't sell me the control arm. They wanted me to buy a complete heater box at a cost of $400.00. I bought a used heater box for $35.00. I just replaced the control arm. So far it is working and it gets really cold.