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This is my 1st post, but I did search for a solution first. ezone you are very helpful (and patient) and I hope you are reading this. I found several posts that were close, but they did not lead to a solution. I am no genius, but I was a mechanic for years and now work as an electrical engineer. I have always fixed my own cars. So here is the skinny:

2006 civic ex sedan, 115,000 miles, manual trans, standard AC (no climate control)

1. AC was working, but my evaporator was freezing up.
2. I replaced the expansion valve, receiver-drier, and evaporator temp sensor (since I was in there).
3. Pulled system down, made sure it held vacuum, and charged system.
4. While charging (AC on max, blower running), with gauges on HI and LO side, I noticed the compressor was not engaging when pressure was "in range".
5. I also noticed neither of the fans were running either. The main cooling fan eventually cycled on/off to keep the engine properly cooled. Condenser fan never turned on.
5. I jumped the relays for the compressor clutch and condenser fan to get them running and finished charging the system to the proper pressure levels. Air nice and cool so system seems to "work".
6. I checked all fuses under the dash and hood - all are good. I also tested all the under hood relays and they are all good (replaced the clutch and condenser fan relays for good measure since I had some).
7. After testing the pressure switch, I found the output (green wire) was 1.2V, which is in the nominal range. So I suspect the pressure switch is fine.
8. I rechecked all under-dash connections thinking I bumped something when I removed the blower assembly to replace the expansion valve. Everything was tight, no bent pins, ...
9. I ran the HVAC control unit self test and it found no problems. My ODB2 scanner is showing no codes either.
10. I popped the front dash cover and checked all connections to the HVAC control unit, everything looked good, no worn wires...
11. Using my probe, I was able to determine that the coils on the fan and clutch relays were not being driven to ground by the ECM. The other side of the relay coils show battery voltage.
12. After lots of research, I found a post with most of these symptoms and it turned out to be the ECM, so I bought a used one.
13. I swapped the memory chips from my old ECM to the new(used) ECM and the car runs and drives fine, but still no AC.

Right now I have:
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* A properly charged, leak free, AC system.
* HVAC control panel that seems to work fine (no self test errors, all lights work as expected).
* Compressor clutch and fans that only run when I jump the relays.
* Main engine cooling fan that turns on/off as the temperature sensor demands, but it does not run when the AC is on (unless the engine is hot).
* An AC system that blows nice cold air, but only when relays are jumped!

UPDATE 1:
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1. I unplugged ECM connector A (the white one), reconnected the battery, and turned the key on (did not attempt to start!).
2. Using my probe, I was able to ground pin 4 (FANL) on the white connector and both fans ran at "low" speed.
3. I then grounded pin 14 (AC compressor clutch) and I could hear the clutch engage.
4. I then grounded pins 4 (FANL) and 5 (FANH) simultaneously. The condenser fan stoped, but the radiator fan ran at "high" speed.
This tells me the circuits for the fans and compressor clutch are fine, including the relays, but the ECM is not sending the proper signals. I find it hard to believe I had 2 bad ECMs, but anything is possible. Any suggestions would be appreciated.

UPDATE 2:
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1. I found this link, which gave some helpful things to try.
2. Testing the thermal protector in compressor yielded positive results (short between BLU and BLU/WHT wires on compressor connector on alternator).
3. Using my probe (with AC on max, blower on) I applied ground to the BLU wire. This sent the proper signal through the thermal protector and to the MICU.
4. The MICU responded properly and sent the CAN message to the ECM/PCM. The clutch engaged and both fans started running !!!! PROGRESS !!!!
This tells me the A/C request circuit through the MICU and to the ECM/PCM is good and the problem appears to be with the request signal coming the from the in-dash HVAC control panel.

UPDATE 3:
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1. I disconnected the connector on the back of the HVAC control unit in the dash.
2. With the ignition on I shorted pin 11 (BRN) on the connector to ground and the fans turned on.
This tell me the A/C request circuit between the HFAC control unit and the MICU is good so I bought a used HVAC control unit. Will update when I install it. I expect it to work....