This shouldn't be this difficult to figure out... it seems like the dealerships are lost unless they have a trouble code.
For example, changing the compressor was throwing parts at the problem. If the old compressor did engage when the clutch had 12v, it makes no sense to replace it with a new one.
If this was my car, I would:
• Verify the compressor ground with an ohm meter.
• Measure the current in the wire going to the compressor clutch using a current clamp. (very easy to do)
If the A/C relay (soldered to the inside of the IPDM/ER) has pitted contacts, you can measure the proper voltage, BUT the contacts may arc and create a high resistance, greatly reducing the current and the clutch can't engage.
- just like when the battery has corroded connections and you try to start the car.
Have you tried the IPDM/ER "Auto Active Test"?
This will verify if the IPDM/ER can control the clutch.
In auto active test mode, the IPDM E/R sends a drive signal to the following systems to check their operation. • Oil pressure warning lamp
• Front wiper (LO, HI)
• Parking lamps
• License plate lamps
• Side maker lamps
• Tail lamps
• Front fog lamps
• Headlamps (LO, HI)
• A/C compressor (magnet clutch)
• Cooling fan (cooling fan control module)
Operation Procedure
1. Close the hood and lift the wiper arms from the windshield. (Prevent windshield damage due to wiper operation)
NOTE: When auto active test is performed with hood opened, sprinkle water on windshield beforehand.
2. Turn the ignition switch OFF.
3. Turn the ignition switch ON, and within 20 seconds, press the front door switch (driver side) 10 times. Then turn the ignition switch OFF.
CAUTION: Close passenger door.
4. Turn the ignition switch ON within 10 seconds. After that the horn sounds once and the auto active test starts.
5. The oil pressure warning lamp starts blinking when the auto active test starts.
6. After a series of the following operations is repeated 3 times, auto active test is completed.
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