2002 Civic AC issues "again"

weav01

Respected
So i have read nearly all the AC issue threads and learned alot. Here is my situation which is similiar to alot but need a little more direction and guidance.
First off AC quit working. Inside blower works and controls show green.
Rad fan/Cond Fan/Compressor do not engage when switch is turned on.
Relays all good (swapped back and forth)
Jumper 12v across pin 1 and 2 of Compressor clutch relay and clutch engages
Jumper 12v across......Rad fan relay and Condenser fan relay and fans begin to run.
Thermal protector measures 3.1 ohms across pin 1 and 3 of the connector.

ECM troubleshooting
I was able to sound out ECM pin E14 to the Compressor Relay pin 4.
Jumpered a ground to ECM E14 and compressor clutch engages
Sounded out ECM B2 to Rad fan/Compressor fan relay pin 4
Jumpered a ground to ECM B2 and both fans begin working.

I have read about Multiplex Control Unit. What is this and where is it. Am I heading in the right direction or did I miss something important.

Schematics that I have found online for this civic are not of the best quality for detailed items but got me in the right areas. https://estore.honda.com/service-express/subscriptions.asp might be a resourse if someone has used it and can give me their opinion. Its $10/day and i assume you can find good quality schematics.

Any Help and advice will be greatly appreciated.
Jeff
 

weav01

Respected
Well thank you. Took me along time to compile that data. Where is the MCU located? I obviously have the ECM pulled out of behind the glove box. Or is the MCU within the ECM? Next those pin letter and numbers are very hard to read, even on the copies of those diagrams that I have downloaded. I had someone else have me check that the pressure switch was showing a ground when the AC was turned on which it was.
 


weav01

Respected
I will check that yellow wire tonite. SO it sounds like that yellow wire goes from the ECU to the MCU? Looks like E24 on that diagram. I have downloaded those civic files. kinda figuring out how to use them. Are the wiring diagrams under a particular section?
 


weav01

Respected
When you said to disconnect the MCU connector...where is that connector located? Under the dash with the fuse panel?
 

weav01

Respected
Thanks again for all the input. Late last night once i got home so did not get to troubleshoot. I did download the manual and isolated the AC pages.
 

weav01

Respected
Well I feel like an idiot. Sometimes the obvious problems is in the shadows while you brain thinks catastrophe and looks for the harder more difficult problem. I decided to push the needle valve on the high/low pressure side. NOTHING. Absolutely no coolant in the system. No wonder. I really appreciate all your direction. I have learned alot about this 'ground' based system, PCM, MCU, relays...etc. Now to track down and see where my coolant leaked from.
 


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