Like most vehicles, my wife's Toyota Matrix turns the A/C on to dehumidify whenever the defrost or defrost/floor settings are selected. Since we live on the wet coast, defrost is used most of the time to keep the windshield defogged. Therefore, the A/C is usually on.
Today I got thinking. The Matrix has a separate A/C switch, so why not modify it so the defrost does not automatically turn the A/C on, and if dehumidification is necessary simply hit the A/C button and leave it on for half a minute?
A quick look at the Matrix wiring schematic revealed that the single yellow wire going into the heat position selector needed to be snipped.
I removed the radio and went in from above because I did not have the tools to unclip the panel that encloses the heater controls.
That's it! It works great. Less A/C time will equate to less fuel consumption.