I feel like my thread has been light on details and pictures for a little while now, so hoping to correct that.
Got my A/C working yesterday.
Pin A27 (blu/blk) on the Insight ECU is "AC ON", which is 12v that passes in series through the climate control and then pressure switch (which regulates A/C line pressure). This is supposed to go into the ECU, which can then decide whether or not to pass on that 12v through pin A17 (red) to the A/C clutch relay.
On the RSX (from which I took my ECU), pin E18 is the clutch output, so straightforward enough, just connect Insight harness wire A27 to RSX ECU pin E18 and the ECU should be able to turn the A/C compressor on and off.
The RSX, however, does not have a dumb 12v signal for A/C, but instead uses a multiplexer for input. Luckily KPro (aftermarket ECU chip) allows reassigning inputs, and one common way to work around this is to reassign the VTEC Pressure Switch (ECU B9, blu/blk) which is not used in JDM motors to an A/C input. Amusingly, the wire colors are the same for VTP on the RSX and AC ON on the Insight harness, so it's blu/blk to blu/blk.
