Depinned engine harness --- now ... ??

[e015475]

You're making this way too complicated.

To turn on the fan to cool the engine, the PCM grounds a external relay based on a temp selected in the PCM tune.

The trinary switch can also ground the same relay when the head pressure gets too high and the fan needs to come on to cool the ac condenser and bring the pressure down.

The fan shouldn't run all the time. It should be modulating the temp in the radiator as required, or be on when the head pressure is high in the ac. The fans shouldn't be running at highway speeds at all, and if they are, it can be an impediment to cooling.

You can disable the PCM stuff in HPTuners and shove a temp bulb into the radiator (or a thermo switch as shown in your drawing) for a stand alone control and wire your trinary switch to ground pin 85, but why when you have HPTuners? It's like killing ants with a hammer - it works but it isn't a very elegant solution and it is just another system to fail.