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Chris (aka-Moose)
Chris (aka-Moose), Technician
Category: Honda
Satisfied Customers: 47942
Experience:  16 years of experience
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I was wondering the charge help?

Customer Question

I was wondering the charge for your help?
Submitted: 1 year ago.
Category: Honda
Customer: replied 1 year ago.
I have a 2003 Honda Civic. The air conditioner is not blowing cold air. The blower is working fine. The a/c buton lights green. I have done a diagnostic test on the unit and I get no blinking of the recirc light. I the condenser fan does not come on and the a/c clutch does not engage. In the under the hood fuse box, when I remove the relay for the condenser fan and a/c clutch and jump pin 1 to pin 3, both the condenser fan comes on and the compressor clutch engages. I have test bypassed the evaporator temperature sensor without any change. I have bypassed the pressure switch with no change. I have multimeter ohm tested the condenser fan and thats normal. Whats wrong with my a/c unit?
Customer: replied 1 year ago.
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Expert:  Chris (aka-Moose) replied 1 year ago.

Based on the tests you have done, if all were done correct then you have confirmed the PCM is not receiving the AC request signal or the PCM is faulty and not sending the command to the clutch relay. If you need the circuit diagram, to check your work, let me know.

You want a excellent 5 star answer & I would like to be rated the same for providing it. Consider I don't know your skill level & I can't see, smell, hear, or touch the vehicle. It may take a few back and forth replies. Try your best to respond with good detail so I can do the same. I normally log in at 3pm and work late. A rating is required. Your rating me, what I type. I am not an employee of this website, nor have control over the fees or the time it took to get a response. If you rate negative or not at all you still paid, but I get nothing. I want you pleased with me and my efforts, so let me know if your experience here has come up short.

Thanks Chris

Customer: replied 1 year ago.
Sorry for the delayed response. I again checked for voltage at the #9 pin connector F under dash fuse box and it had no voltage. Car running, ac on or off, still no voltage.
I then checked for continuity between #9 pin and the ac pressure switch and there was none. I don't think its the same wire though. The blue wire at the pressure switch and the blue/wht from #9 pin connector F look to be 2 different wires. So its hard to think I would get continuity there. I did try to bypass the pressure switch and had no response. The pressure switch ohm tests normal.Does #9 pin connector F receive signal from the PCM that goes to the clutch relay or the #2 terminal presssure switch?Do I have a bad multiplex?I also wanted to share I have test the ac pressure circuit connector A pin 4 and there is voltage. Started the car and the ac clutch did not engage nor did the condenser fan come on.I also tested voltage in the under the hood fuse box terminal #1 and fuse intact with positive voltage. I have tested all relay there and all test working my multimeter for ohms and I do hear a cliking with voltage change when testing with battery power.I am still baffled by the fact I can bypass the relays and get the ac condenser fan and compressor clutch to work and blow cold air. I agree something is not getting the signal to something else, but those 2 things seem to center at those relay junctions.Not questioning your PCM idea, but could you explain why it seems the center of my problem seems to center around those 2 relays? How would it be determined if I had a bad multiplex (vs) PCM?Thanks for your patience!!!
Customer: replied 1 year ago.
One more thing I just found reading another post on a post on clubcivic.com. There was a description of the under hood relay terminals. The guy said thatterminal 2 is always hot
terminal 3 is hot only when the key is on
terminal 1 and 4 are never hotIn checking just now, I found the compressor clutch relay terminal to be just that. In working order.But in the condensor fan relay terminals, the #1 2 and 3 terminals work correctly bu the #4 terminal was hot with the key on.Should that terminal be hot with the key on? Does that help you any?
Customer: replied 1 year ago.
FYI, that terminal 4 stays on when the key is on, whether the ac is on or off.
Expert:  Chris (aka-Moose) replied 1 year ago.

Auto or manual AC?

Sedan or coupe?

Customer: replied 1 year ago.
Manual ac - push the ac button ( I did'nt know in 2003 they had an auto ac? ) When the blower knob is off, system in off. When the blower knob is on high - ac button off, blows ambient air. Push the button - green light comes on, still ambient air.2003 Civic Coupe
Expert:  Chris (aka-Moose) replied 1 year ago.

Below are the links I will be using.

https://dl.dropboxusercontent.com/u/90220402/03civicac1.pdf

https://dl.dropboxusercontent.com/u/90220402/03civicac2.pdf

Based ion the tests you have done its the ECM or the multiplex. Do you have access to a diagnostic tool to see if either of those are getting the AC request signal, resulting in not grounding the clutch relay pin 4?

Customer: replied 1 year ago.
I don't have a relay circuit tester. I have a multi-meter. Would that be sufficient?
Expert:  Chris (aka-Moose) replied 1 year ago.

The multi meter can only verify the relay is not getting a ground command via OHM testing but it does not have the ability to see if the modules are getting and receiving signals. We know its not sending a signal out since the relay is not closing.

Customer: replied 1 year ago.
The condenser fan relay is the one not closing right since pin 4 stays hot, right?
Customer: replied 1 year ago.
You know its a coupe not a hatchback?
Customer: replied 1 year ago.
The pdf's you sent just say hatchback
Expert:  Chris (aka-Moose) replied 1 year ago.

Neither fan relays or the clutch relay appear to be getting the ground on pin 4, which is why none are activating. We just need to know if the multiplex is telling the ECM you want the AC on.

Expert:  Chris (aka-Moose) replied 1 year ago.

Below are all the different HVAC options.

https://dl.dropboxusercontent.com/u/90220402/civicAC.pdf

Customer: replied 1 year ago.
Does the multiplex communicate with the PCM through the under hood fuse box or directly under the dash?My under dash connector F pin 4 is a blu/wht wire, according to the pdf page 2, the only blu/wht wire goes between the blower motor and the blower motor relay pin 4. Is that your reading as well?
Expert:  Chris (aka-Moose) replied 1 year ago.

https://dl.dropboxusercontent.com/u/90220402/civiccommunication.png

Customer: replied 1 year ago.
do I need to see if multiplex E10 is getting voltage from the PCM when the ac is turned on?
Expert:  Chris (aka-Moose) replied 1 year ago.

You can not test a communication wire for power or ground. Its a signal it sends not a power or ground. Its like comcast in your home. One wire brings you 1000 channels, 100 gigabytes of internet and phone, and there are hundreds of other homes all on that same one single wire.

Customer: replied 1 year ago.
Oh, ok.So I need to find a relay tester then? Would that tell us if the problem is with the PCM or the multiplex? Or how do I find that out?
Customer: replied 1 year ago.
I am still puzzled as to why when I jump the pins 1 to 3 on both relays the system works? In that case would that tell us if its the PCM or the multiplex?
Customer: replied 1 year ago.
BTY thanks for your patience with these questions.
Expert:  Chris (aka-Moose) replied 1 year ago.

You need a diagnostic tool. A test light and multi meter can test a relay which you have already done. When you jump the pins 1 and 3, your bypassing the relay and the modules.

Customer: replied 1 year ago.
The diagnostic tool your referring to is a relay circuit tester?
Expert:  Chris (aka-Moose) replied 1 year ago.

I have no clue what a relay circuit tester is. I have never heard of that tool nor seen one. The diagnostic tool is called a HDS diagnostic tool.