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I have a 2007 Honda civic si 2.0 AC is not working. all

I have a 2007 Honda...
I have a 2007 Honda civic si 2.0 AC is not working. all fuses are good and the green lights on the dash come on. there are no fans nor clutch engagement. However, if I ground the red wire at the compressor the fans and compressor start working. I have evacuated and charges the system to specs. I have also switched out the black ac relay to no avail.
JA: Have you checked the fuses? The dashboard bulbs?
Customer: all fuses and I havent checked the bulbs. Bulbs ,it has a backlit dash and it's lit
JA: Are you fixing your Civic Si yourself? What have you tried so far?
Customer: evac and recharge . self test on control and indicated no codes. scanner reads no on ac command until you ground the red wire at compressor
JA: Anything else you want the mechanic to know before I connect you?
Customer: no
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Customer reply replied 4 months ago
I should add that after disconnecting and connecting the harness by the master cyl the ac would work for a couple of seconds then shut down. it was very sporadic then stopped all together again. I shook the harness and moved it around but could not get it to duplicate. when it did work it wasn't shutting off on pressure . I had gauges on it and the high side would only go to 100 or so. Again very sporadic. it seems like a ground issue . But as for now. I need help
Answered in 40 minutes by:
7/13/2017
Mechanic01
Mechanic01, ASE Certified Technician
Category: Honda
Satisfied Customers: 1,174
Experience: Owner at Baltic investments
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Hello my name is ***** ***** I will be assisting you with all of your vehicle questions today. Give me one moment while I review your question and come back with a answer. Please be aware I do not know your skill level or abilities so I will be asking a lot of questions and in a lot of cases we will respond to each other quite a lot before we find a solution. As far as phone calls are concerned that is the system prompting you, not me, and they do cost more money, I prefer text but in some cases a phone call is required.

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Customer reply replied 4 months ago
k

1. Unplug the A/C compressor 3 pin connector and test the A/C thermal protector which is on the A/C compressor. Determine if the thermal protector is open; it should be a closed circuit and show continuity across the wires, if not, the thermal protector is bad. If a scan tool indicates A/C switch "ON" and A/C clutch "ON", then skip this test and look for a faulty A/C clutch relay or A/C clutch.

2. Test the voltage on the BLU/WHT wire at the thermal protector to determine if it has a 12 volt reference, if not, check for an open wire between the under dash fuse box and the A/C compressor. If there is a reference voltage, backprobe and ground the wire with the engine running and the blower fan turned on and see if the compressor turns on. If the compressor turns on, this would indicate that the A/C request circuits to the Powertrain Control Module (PCM) are good and the problem would be with the A/C request ground signal provided by the from A/C control panel.

3. The A/C control panel should apply a ground to the Red/Black wire at the thermal protector, when the A/C switch is turned on. If the control panel is not grounding the wire at the thermal protector, check for an open wire between the thermal protector and the A/C control panel. There may be a bad input to the control panel if the Red/Black wire tests good.

4. If the compressor did not turn on in test #2, then check for power to the A/C compressor clutch and look for a faulty clutch or a faulty A/C clutch relay.

On this system, the A/C compressor request circuit is somewhat complicated. The A/C request signal is sent to the PCM via CAN communication from the instrument cluster. The instrument cluster receives an A/C request signal from the underdash fuse relay box multiplex control unit. The underdash fuse relay panel multiplex control unit receives its request signal from the A/C control panel but that signal has to pass through the thermal protector on the compressor. Hint: the A/C control panel will not give a compressor request signal when the blower motor is inoperative.

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Customer reply replied 4 months ago
okay . I tested the thermal protector and it has continuity. However the wires on the plug are Rd/blk , rd/white/Grn/white, It looks as if the green and white one provide 12v to the compressor. the fans and compressor come on when 12v is applied to the green /wh wire I see there is a difference with the SI wiring.Which this is. BTW all the blower speeds work and I changed the ac module with a know good one and the same result
Customer reply replied 4 months ago
sorry gr/rd
Customer reply replied 4 months ago
Edit: If I apply 12v to the rd/white wire at the compressor connector the fans and compressor come on.

What did the scan tool say when you were doing the test

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Customer reply replied 4 months ago
it said ac switch (on) clutch (on) disconnect and they go to off

If im reading everything right you have a clutch relay problem

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Customer reply replied 4 months ago
From what i see its a black relay in the distribution box. I changed it out and still nothing. unless on the SI edition it's somewhere else

im gonna have to brew on this for a min, such a complicated system

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Customer reply replied 4 months ago
brew on it til monday.. thank you

The A/C control panel should apply a ground to the Red/Black wire at the thermal protector, when the A/C switch is turned on. If the control panel is not grounding the wire at the thermal protector, check for an open wire between the thermal protector and the A/C control panel. There may be a bad input to the control panel if the Red/Black wire tests good.

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Customer reply replied 4 months ago
will do

.

Mechanic01
Mechanic01, ASE Certified Technician
Category: Honda
Satisfied Customers: 1,174
Experience: Owner at Baltic investments
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Customer reply replied 4 months ago
Shawn , you have been a great help. However I don't want to waste you time. The customer had to use the cars but bought it back the other day. I accessed the control panel and seen which wire went to ground when the switch was turned on. as soon as I probed the red/wh wire out of the panel the compressor and fans started working and acutally worked with the switch . I had one of those red/green light testers with the diodes in it. I disconeccted it and the ac kept working for a while. then it would stop. I probe the wire again and she works like a champ. so I left the dam test light in the wire attached to a ground and off he went. I just got a call the ac stopped working. I am pretty convinced that its the control module even though I have one from a regular civic. I will try to keep figuring this thing out and will rate your service excellent

Thanks for the great rating! Let me know if you need any more help ill do anything I can to get you what you need

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