kaipederson

Hey all, just bought my first Civic, a 2002 LX 5 speed Coupe with 160k on the odometer. I owned two Wranglers beforehand, and I did a fair amount of work on them (lots with the CJ). The biggest issue I've had since I got the car a few days ago is that the A/C won't blow cold air. I read up on the topic and tried to find as many threads that were applicable to my 7th gen, but I have had trouble finding one that has the same problems as mine. When it wasn't blowing cold air before, I figured I had better check my frion, and when I attached the gauge to the low side, I got a reading of 100 psi. I was initially puzzled, but then found that the compressor clutch was not engaging. Lots of reading later, I went to work on it. I was confused, as neither my compressor clutch nor the condenser fan would kick in. Checked fuse #1 under the hood, and #14 from in the car, and both were fine. Shuffled the relays around, and still nothing. I jumped terminals 1 and 2 on the Compressor clutch relay socket, and I was able to get the fan to kick on, but no clutch. I then jumped terminal 2 on the 3 wire Compressor clutch connector to the battery and was able to get the clutch to engage. I get voltage from terminal 1 on the connector but no others. Any ideas? A/C is brand new to me coming from Jeeps, and I'm not afraid to say this is my first time doing A/C work. Any help would be greatly appreciated!! If I have not been clear enough/need to provide pictures/etc. please let me know. Again thank you so much for the help!

ezone

ezone

I think you probably jumped the fan relay, not the clutch relay.


First, go back to the fusebox and find the clutch relay and recheck there.

You have a 3 wire connector at the compressor. The center wire runs the clutch.

The other 2 wires.....Grab the engine harness side connector (not the compressor side connector)..
Turn on the AC on the dash..
Check for a ground on either wire.

Got a ground or not?

Now use a jumper wire to supply a ground to the other wire.
Do the fans kick on now?



Here's a link for you to read where we kinda walked through a lot of the testing and ended up with a bad thermal protector.
https://www.civicforums.com/forums/3...t-working.html



EDIT: And a diagram

kaipederson

Right you are, my bad.



Clutch kicks on without a hitch. Also tested both fans, both work.


Blue/white has a ground.


Didn't have a long enough wire on hand to test with, will test tomorrow afternoon. After reading the thread you posted, I am assuming that the Blue/white is the one that should be grounded?



Thanks a ton for the quick response and helpful info. I appreciate it!

ezone

Look at the diagram.
The HVAC controller (at the bottom of the page) applies ground to the blue wire when the AC is turned on. This is the AC request signal to the PCM.

This signal has to go through the pressure switch, the thermal protector on the compressor, and the multiplex unit before it reaches the PCM. Any of these can break (open) the request circuit if something is wrong. You are just trying to figure out if that request signal (ground) is lost somewhere between the HVAC controller and the PCM.

You measure for ground on one side of a switch (for example), and you measure for the same ground on the other side of the switch if it is still connected.
But if you have to disconnect that switch, then you can supply your own ground to test, effectively bypassing the switch. Or jumper across the two sides.


Did that make sense?


Once the PCM receives the request and decides it's OK to engage the compressor, the clutch relay is turned on along with the relays for both fans.
You said your fans did not run when the AC button was pushed so I assume the PCM is not getting the AC request.

kaipederson

I believe I do. So when the Blue/white wire is connected to the red wire (which is always hot) on the opposite side of the switch, the PCM is being bypassed in the circuit, and if that works, it would confirm that the issue is with the PCM or MCU? And if it doesn't, check thermal protector? Thank you!

kaipederson

So I grounded the Blue/white wire, and I got both fans to kick on, but not the clutch. So I went to the other thread and proceeded to check the outside two red wires on the connector from the clutch side. No continuity. Should just be the thermal protector then, correct?

ezone

Red between pressure switch and thermal protector shouldn't be hot. The system is using a ground as the request signal.


Yay.
Was there a ground at the red wire (#3 terminal)?
Because the clutch was disconnected. Right?
Sounds like it.

kaipederson

Red wire was grounded, went ahead and ordered the thermal protector. I'll let you know how it goes when it is installed! Is there any magic way to get it in, or should I just pull the alternator and power steering pump? Again, thank you for all the help ezone

ezone

No tricks to it that I'm aware of. Remove PS pump and alt to get access to the top of the compressor, dig out the old part and stick the new one on with a dab of RTV silicone.

Last couple posts in this thread: https://www.civicforums.com/forums/36-mechanical-problems-vehicle-issues-fix-forum/359757-2004-ex-ac-not-working.html#post4664075