a/c will not turn on

2002 HONDA CIVIC
175,000 MILES • 1.7L • 4 CYL • MANUAL
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PWJUNEAU
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  • 3 POSTS
This question goes beyond the basics.
A failure of the mcu, created dome light, door locks, dash brake light, remote door locks, etc.... failures.
A new mcu, honda part matched to the vin has been installed.
All inop functions mentioned above returned to correct operation.

Except, no A/C button response.
Wiring verified for compressor pressure safety switch to mcu is good as well as , evap temp sensor verified,
Started chasing the A/C button function, light green wire from the dash control.
Then, silly me, Honda duplicates wire size and color.

My feeling, and I could be wrong, is the A/C control system does not see the low true function of this button.

Any help would be greatly welcomed!
Thank You!
May 12, 2014 at 9:49 PM
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WRENCHTECH
  • ✓Experienced Mechanic
  • 20,760 POSTS
They have a lot of problems with the control heads in those models. You are going to have to trace power supply into the control head to see where you are losing it. It ay be the head itself.
May 12, 2014 at 10:08 PM
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PWJUNEAU
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Thank You! For your fast reply!
That is what we thought as well. Maybe a control head issue.
Tried another one, not sure of the origin.
On the connector that leaves the control head.....
There is a green wire with 2 silver markings, this wire changes from Battery voltage to near ground, when the A/C button is pressed, I think the signal is working from the control head....Unless, there should be switch action on another pin.

I am fairly convinced the signal is lost to its destination, where does that wire go next, after it leaves the control head?

Thanks!
May 12, 2014 at 11:29 PM
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WRENCHTECH
  • ✓Experienced Mechanic
  • 20,760 POSTS
Let me know if there is anything you don't understand https://www.2carpros.com/images/external/120066631.gif
May 13, 2014 at 7:29 AM
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PWJUNEAU
  • MEMBER
  • 3 POSTS
Thank You!

The diagram helps, problem solved, heater control panel replaced.
I also found out, if the A/C led comes on, the switch is OK!
Have a nice day!
May 13, 2014 at 11:25 PM
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