I made a few changes in the logic circuit. I added an additionnal condition for the coolant temp.
The vehicle has two engine coolant temp sensors so why not tap both ? By monitoring both sensors I can create two distinct trigger temps for half-open and fully open before the fans turn ON.
From obervations on the scanguage, the reported coolant temp usually moves in 2 degC steps. I have to consider that when selecting the desired trigger temps.
Below is the new logic diagram :
This is the actual, functional breadboard circuit. Logic works as intended.
Coolant below 96c : Shutters Shut
Coolant above 96c : Shutters Half-Open
Coolant above 100c : Shutters Fully-Open
Should any Fan be ON, regardless of coolant temp : Shutters Fully-Open. My goal is fully open before the Fans come ON. I still need to figure at what coolant temp they turn ON to better tune the trigger temps in the logic circuit.
This condition adds a fail-safe operation should the coolant sensors fail, which is unlikely..
Cheers.