So I bought this used car from somebody and the guy who had it put ground directly to the relay pin that is supposed to be grounded by the ECM. Luckily I have gotten experience with this kind of issue before on a infiniti g20 2002 car and it was the ECM. But on this car I am confused, the part that I did not understand is why the AC Clutch pin is reading 14v and is not reading 14v on the connector to the AC? I checked for continuity and it is ok. Also ECM PIN 17 continuity ok. I have never been so confused before, the ECM is not grounding the relay, it reads OL in ohms mode when AC is on. I did check volts on the AC pressure switch and I get 4.7v on the BLUE/WHITE wire and it does have freon. I will post back later if I find anything.

 

Does the clutch relay get battery voltage on pin 4? If not, check dash fuse 17. If so, the relay may be bad.

 

Ok I did check fuse 17 and fuse is ok. About PIN 4, not sure which one is PIN 4, which is why I drew it. But now I can kind of see where 14v might be coming from, not sure if is the diode. Also I did change relay and it wasnt the issue. If the ECM is not sending ground, more than likely I think it could be my issue, unless I am missing something.

 

Unplug ECU connector A. Turn key to ON(II) with A/C button OFF. Do you measure battery voltage at ECU pin A17 in the unplugged ECU connector?

Have you used a multimeter to test whether the A/C pressure switch is closed?

When you turn key to ON(II) and turn the A/C and blower on, does the condenser fan run?

 

Pin A15 on Honda Civic 2000 says that it is an empty slot. Are you sure I am supposed to check this one?

 

My apology for the typo. I should have typed pin A17.

 

I figured it out, the ECM was bad. Exactly to what happened to an infiniti g20. Here is the video:

 

Nice work!

Can you post pictures showing the exact location of the bad component and a link to the replacement part?

Any idea what caused the component damage?

 

Right now all I have is the video. The part number is STA415A and I replaced it with NEC UPA1560H. It just has to be an N-Type mosfet. I ordered the part through ebay. Not sure what caused the issue.

 

Ok I have an update. I did put the ECU back and it did turn on, but now it does not want to turn off. So I tried the other ECU that I bought and for some reason that one did not want to turn on. So then I started checking voltages with the car running PIN 17 had 14v and when I checked PIN 27 (ACP) the clutched turned on by touching it with my test lead and it has 4.7v, I am not sure how much is supposed to be. So I am suspecting I have an issue with AC Pressure Switch or AC Pressure switch cable.

 

I checked continuity Blue/White wire from pressure switch connector to PIN 3 on condenser fan relay and it has no continuity, could this be my problem?

 

^When either ECU is installed.

 

This test result indicates that the Blu/Wht wire has an open. Also test the wire for a short to ground.

The test does not check continuity across the pressure switch.

Voltage at pin 27 should be ~5V, so your reading is fine.

 

Ok, so I found the open wire on the Blue/White wire from AC Pressure switch.

I fix the open wire and it now works like normal.

 

Great work!

 

Wild goose chase. But this is a given when it comes to electrical problems.