The pressure switch is indeed a dual switch. There are 2 A/C power relays, the first (relay B) providing power to the second (relay A), but the second (relay A) is triggered by a third relay contained within the ECU. Simple, eh? Nope.

The condensor relay gets power from Relay A, but is triggered by the dual pressure switch.

Ditto on downloading the FSM to get the schematic. It is indeed a complicated set of circuits, but understandable if you take your time and trace it all the way through.

Once you grasp it all, it's clear as a bell, but right up to that point, it can be quite muddy.

The thing that's easy to miss is the ECU relay control. When I replaced my OE ECU with Megasquirt, I installed a separate relay, triggered by the (+) signal from the ECT switch to provide a (-) trigger for the A/C Relay A coil.

Frank