Clutch/pulley wobbling and making load racket. Replaced compressor, dryer, and expansion valve. Flushed system. New compressor had two oz. oil in it. Put 2 oz. back in comp. added 2 more to comp and 3 oz. in dryer. Replaced all o rings. Pulled vacuum for 30 minutes. Charged with 12 oz 134. Compressor will not come on. Ran 12 volt straight to comp to get it on. Low side pressure 20 psig high side 300 psig. Why would pressure be so high and what else could prevent comp. from coming on?

 

Check for blown fuses in the A/C compressor clutch circuit. Do the fans run?

 

No, fan does not run. 20 amp fuse good under hood. Swapped relay still nothing.

 

You need to test two separate fuses:

20A hood fuse 1
10A dash fuse 14

Use this method:

https://honda-tech.com/honda-civic-d...fuses-3079359/

 

Tested per instructions. Both good.

 

A Blu/Wht wire runs from the multiplex control unit to the A/C pressure switch. If you unplug this switch and ground the Blu/Wht wire in the free connector, does the A/C clutch engage and the condenser fan run with the key in ON(II)?

 

Grounded blue whit wire. Nothing. I jumper end the low pressure switch and still nothing. Only way I've gotten the comp to come on is 12 volt straight to comp connector.

 

A Yel wire that activates the fan and clutch runs from the ECU to the multiplex control unit. In the connector that plugs into the multiplex control unit, ground the Yel wire with the key in ON(II). Do the fans run and the clutch engage?

 

Cooling fans are coming on and off but comp has to be ran off 12 volt wire to connector

 

With Yel wire in multiplex control unit connector grounded?

 

Multiplex is the control switch on the console?

 

Diagrams for the 02-03 Si:

 

Si A/C system circuit diagram:

 

Thanks for the help. I won't be able to work on it for a few days. I'll check multiplex as soon as I can.

 

Not sure where the yellow wire is. Back (engine side) or front of multiplex ?

 

Connector E is located at the front of the dash fuse box.

 

Thanks. Had something come up. Won't be able to look at it until later in the week.

Finally able to work on this problem some more. Do you ground the yellow wire with the connector plugged in or unplugged? I tested it with the connector plugged in and still nothing.

 

Either way.

With key in ON(II)? Fans don't run and compressor clutch does not engage?

 

Correct. Nothing.

 

Unplug ECU connectors B and E.

Turn key to ON(II).

1) Ground the green wire at ECU connector pin B6. Do the fans run?

2) Ground the red wire at ECU connector pin E18. Does compressor clutch engage (click sound)?

 

Yes and yes

 

Use a multimeter to test whether the Yel wire that runs between ECU pin E24 and MCU pin E10 is broken (no continuity between endpoints).

 

Green wire grounded fans run.
Red wire grounded clutch engages.

 

 

Yellow wire shows to be good.