[jorgensensc]

Ok, help me understand please. What year vehicle and AC system? Why are you going through the PCM? The trinary gives power to the compressor as long as the head pressure isn't too high. A proper trinary switch also gives ground for fan relay when the head pressure reaches a certain threshold. That is why the fans won't run when driving on the freeway( in a properly working system of course). Contrary to popular belief it is not a great idea to have the fan automatically come on when the a comes on. Such as while driving down the freeway and the system doesn't need the head pressure reduced.

Shawn