Are two of the A/C relay terminals supposed to be hot when car is in off position, or one terminal hot (battery voltage) and one cold?

Thanks, Steve. I'll test the ECM.
I've attached the terminal assignments for the AC Control Module

A few items I'm noticing after previous tests:

1. Interior Temp Sensor power supply shows 3.5v (should be approx. 5v) - (B282) 5 to 15
2. Evap Sensor power supply shows 3.5v (should be approx. 5v) - (B282) 13 to 15

*Could this be an issue?
**Is it worth looking at the (i3/B38) 11 connector for a short?

Versus:
3. Mode Door and Air Mix actuators showing 5v (B282) 8 to 15

4. Mode Door actuator power supply cuts out: 10v down to 0.5v
(B283) 7 to Chassis GND & (B283) 17 to Chassis GND
5. Air Mix actuators power supply cuts out: 10v down to 0.5v
(B283) 8 to Chassis GND & (B283) 18 to Chassis GND - Passenger Side
(B283) 9 to Chassis GND & (B283) 19 to Chassis GND - Driver's Side
*Is this normal operation?

Think it's figured out. I should have started with these tests. But lesson learned.

ECM:
A/C On Switch [from the AC Control Module] (B137) 17 - normal operation
A/C Relay Control (B135) 33 - normal operation

*A/C Middle Pressure Switch (B137) 30 - battery power when A/C is on, and off (should cut to 0v).

One Correction from previous post on ECM.

ECM Terminals:
A/C On connector terminal (B137) 17 [from the A/C Control Module (B283) 6] - normal operation
*A/C Relay Control (B135) 33 - Battery voltage is present when A/C Power Switch is off (good), and when it is on (bad)
A/C Middle Pressure Switch (B137) 30 - Battery voltage is present when A/C Power Switch is off (good), and when it is on (bad)

When the A/C is switched on from the Control Panel/Head Unit, via the A/C Control Module, both ECM terminals [(B135) 33 and (B137) 30] should cut to 0v, they do not.

If the A/C power signal coming from the Control Panel to the A/C Control Module (B283) 6, to ECM (B137) 17 [battery voltage when ac is on, zero voltage when it is turned off] is functioning normally, would that mean the issue is not in the AC Control Module (or anything preceding the signal from (B283) 6? Isolating the problem to the ECM?

Please correct me where I'm misinterpreting:

Step 1: Back probe (B135) 33 and jump to Chassis GND.
Step 2: Unplug pressure sensor connector and use the multimeter to test continuity across (B10) 3 and 4?
Step 3: Plug in the Pressure Sensor and test the A/C operation with a manifold gauge?

Much appreciated, Steve.

Even though it's a brand-new compressor in the car, I decided to run the Lock Sensor diagnostic flow today. Got some puzzling (to me) results in Step 7 (attached pics). Anything to dig into here?

I found two loose terminal blades (F37) 16 and (B143) 14 in my Main Fuse Box (they appear to be physically connected/one unit) - pushing one blade will directly move the other (the blades are inline across two connectors).

In Step 7 of the attached A/C Lock Sensor diagnostic flow I measured the resistance between two sets of terminal blades as well as the corresponding connector terminals on the fuse box and kept getting O.L. For everything.

1. Are the loose terminal blades a factor in not getting a continuity reading?
2. If yes, are they affecting the signal to/from the A/C Lock Sensor?
3. Is the O.L reading in Step 7 related to the ECM?
4. In the attached A/Csystem wiring diagram the fuse box terminal [from the Lock Sensor] (B143) 14 connects to the ECM via (B135) 23 which looks to be the Camshaft Position Sensor GND - anything here? - I'm guessing that the lock sensor is syncing with the camshaft position sensor.
5. Could the Camshaft Position Sensor(s) be affecting the A/C system via the Lock Sensor?

Thank you!

Thank you for all the teaching on this.

With ECM AC Relay Control (B135) 33 jumped to Chassis GND, the AC Compressor fires up and blows cold.

Should I order an ECM and get it programmed?

*After some conversations with a local mechanic and another friend, it appears that if you added an iPod 1/8in jack kit to the stereo (which I did back in the day - Jazzy Engineering), it can affect the ECM negatively. I also added a cheap Bluetooth extender to the hack. Maybe this caused the ECM issue?

Thanks again, Steve.

I swapped in and tested a functioning head unit I pulled from the savage yard and two other AC Control Modules all to no avail.

I'm going all in on broken ECM.

Will do.

If I were to put a scan tool on the car (before swapping the ECM), what would I be looking for exactly?

Hi Steven,

Bought a new ECM from Subaru.
Got it flashed today, put it in at the dealer, and AC worked as I began to drive home.
Big smiles.
Then AC quit 10 mins into the drive.
Got home a bit frustrated.
Ended up noticing a bunch of corrosion on the battery ground lead and terminal.
Cleaned both thoroughly.
AC now works.

Was it the corroded ground lead the entire time? Or just a needed reset (battery disconnect) on the new ECM?

It's been an education.

Thank you for your time and attention.