Air Conditioning wire schematics

ahefner1964 · Aug 13, 2025

I have a 90 D150 that I have just installed a 360 Magnum with Fitech fuel system.

I know the original computer system from the factory that controlled the fuel injection also controlled the AC clutch engagement.

Since I am no longer using the original computer, I need a wire schematic for the AC system so I can devise a work around to engage the AC clutch (I want to use the original AC controls in my dash to do this)

Anyone know a source for this wire diagram?

volaredon · Aug 13, 2025

I don't think the ac goes thru the computer

ahefner1964 · Aug 13, 2025

I do know that the relay that engages the AC clutch goes to the computer… and if I ground that wire to the computer the clutch will engage.

ahefner1964 · Aug 18, 2025

I found a second wire from the computer that goes to the thermal control, through the pressure switch, then through the in dash AC control.
Connecting both of the wires from the computer together will allow the AC to work normally without the computer.

Air Conditioning wire schematics

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