Diagnosis of this circuit is methodical and relatively easy. I'm a bit confused by some of the wording you're using, so here's how you can work through the compressor and relay sides of the circuit to determine what the fault is:

1) On the compressor side of the circuit - install a test light in place of the clutch coil, making sure you have good contact. Install jumper wire between pin 30 and 87. The test light should come on (the diagram you posted shows direct battery voltage, so the key shouldn't have to be on, but if it doesn't light, try turning the key on anyway in case there's a discrepancy in the diagram). Start wiggle testing the harness between the fuse box and compressor, making sure to put extra stress on any area where the the harness branches off. If the test light starts flickering, there's an issue somewhere in the harness:

-Disconnect the test light from the power side of the clutch connector - connect it directly to battery positive terminal so the test light is grounded through the clutch coil connector. Wiggle test the harness again. If the light doesn't flicker, reverse the connection so you're grounding the test light directly to the battery and powering it through the clutch connector. Wiggle test again. If you find an area that causes the light to start flickering, that's where the fault (intermittent open circuit) is isolated to.

2) If the compressor side checks out OK, reinstall the relay, but leave the test light installed in place of the clutch coil. Insert a pin into the back side of the PCM connector at pin 11 of C3, the clutch coil control circuit. You'll probably have to remove a plastic cover to do this which usually also means disconnecting the PCM - make sure to unhook the negative battery cable before doing so, then hook it back up once you're set up. Here's the different positions you need to be checking and what you should see at each:

A) Key on, Engine off, AC button off - 12 volts
B) Engine running, AC button off - 12 volts
C) Engine running AC button on - Less than 0.5 volts

If you have less than 0.5 volt with the engine running and the AC button on, you should see the test light come on. However, it will only remain on for a moment because once the PCM sees there's no change in the pressure, it will disable the relay. All you're looking to confirm with this is that the PCM is commanding the relay on. If PCM control is verified, you need to set up the test light to perform wiggle testing on the PCM control side of the circuit. I recommend just unhooking C3 and providing a direct path to battery ground from pin 11, then install the test light as a jumper between battery positive and pin 85 at the fuse box.

 

Thank you very much for taking your valuable time to respond to my post. I remember that the PCM had a lifetime warranty, from when I had it replaced on 2011. Before I read your email, I had already removed it and sent it the mail for a replacement. Will see when the replacement gets here, if the PCM was the actual culprit of the problem. If the PCM is not the issue, I will follow the steps you listed above to find the problem. I will post here the results as soon as I get the PCM installed.

Thank you.

 

 

I had other symptoms, but thought it had to do with something else. But now that you mentioned it... I think maybe all these symptoms could be PCM related and they are all intermittent like the clutch not engaging.

One symptom was the car revs going low feeling like it would shut off. It was intermittent, but I replaced the idle air control valve, but I still had the issue. Another was the headlights flashing on/off rare but intermittent. I know when I got the computer I got emissions EVAP codes that I didn't have before, but since the car was old, I assumed they started.

I hope that these symptoms are all PCM related.

 

Here is the UPDATE:

I got the refurbished PCM under warranty from previous purchase and the issue is still there. I finally found something that I did not notice before. After I installed the computer, started the car, turned the A/C on..... and the clutch did not engage. I unplugged the compressor and reconnected, turned the engine on and the clutch engaged. So if the compressor start working again after reconnecting it, then something is wrong with the connection. I took the car for a drive and the A/C clutch disengaged why I was driving and never came back on. When I got back home, I got a long stick and as soon as I moved the plug the clutch engaged. If I kept tapping the plug I notice the clutch engage and disengaged.

My guess is a loose ground on the compressor, which I am going to check tomorrow. Has anyone experience this issue before?

 

You don't need to guess, because you just diagnosed the connector as the problem. There may still be a problem with the wiring, but you won't know that for sure until you repair the connector.

Any parts store should be able to get you a pigtail assembly to replace it. It's a very straight forward repair - just make sure to pay attention to the plug orientation so you splice the wires correctly.

 

Here is a video of my exact same issue and how to repair it. Thank you for all your help GumbyRT..... Really appreciated.

 

You're welcome.

 

I know its been a while. But just wanted to come back and add some additional information for anyone that may have this same issue. I did not have to replace the Connector. In the process of testing the connector for 12v and ground, I was the one that caused the problem. The Multi-meter prongs I was using were large and while trying to insert it into the connector, I pushed up a metal piece and it was not making contact. I used a pick to push the metal contact down... that way it was a close connection. After I did that, the issue was solved.

Basically I caused the issue in the process of testing or.... while removing the old compressor I may have damaged the connector. But I was able to repair it and not have to replace it.