There is a way to make it possible to turn the compressor Off when you have the windshield vent selected.
There is an important distinction between defrosting
Defrosting is pumping warm air onto the inside of the windshield so that it melts the ice on the outside of the windshield. There is no reason to have the AC compressor running in order to do this.
Defogging is pumping dry air onto the inside of the windshield so that it pulls condensation (fog) off the inside of the windshield. Temperature of the air is not important, just that the air is dry. The AC compressor must be cycling in order for the air to be dehumidified as it passes over the AC evaporator.
If you would like to be able to turn off the AC compressor in the winter time so that you can defrost your windshield in the morning, without running the AC compressor, do the following:
NOTE: This hack cannot be undone in the same manner as it was changed. To return to the factory settings, you must disconnect the battery.
Step 1: Turn the ignition switch to the ON position (you do NOT have to start the engine).
Step 2: Turn the fan knob to the OFF position.
Step 3: Switch to the FACE ONLY vent mode.
Step 4: Turn the temp knob to the COLDEST setting.
Step 5: Turn the ignition switch to the OFF position.
Step 6: Hold down the RECIRCULATION and A/C buttons simultaneously.
Step 7: While holding those two buttons, turn the ignition switch to the ON position again.
Step 8: Keep holding the buttons, and the yellow light on the RECIRCULATION button will begin to flash after a few seconds.
Step 9: Keep holding them down until the yellow light stops flashing/goes solid, then release them.
Step 10: Test it: Turn the fan back on. With the radio off and the fan on the lowest setting, switch to either DEFROST mode and listen carefully for the condenser fan to kick on. Now, push the A/C button. You should hear the condenser fan shut off, which means the hack was successful. If it doesn't shut off, then something wasn't done correctly.
After the above has been done, when you turn on the 'defrost/defog' mode, or the one along with the foot vents, the AC compressor will come on and is indicated by the green light on the AC button. To turn off the AC compressor, hit the AC button and the light will go out and the compressor will disengage whereas before you could not disengage the compressor when either of the defrost/defog settings were chosen even if the AC light went out.