bryanwood74

I did an ls1 conversion into my thirdgen camaro, and used a standalone PSI conversion harness with no AC provisions. Pocket - a member here built a 4th gen harness to use on my car with the ls1 compressor, and connecting to my factory harness for AC, and pins on the computer (Red/Blue) that had to be added. It was plug and play but when I turn my ac on the compressor doesn't start, and I can manually jumper the relay and it kicks on. So I am thinking maybe its my tune setting?

I am using a pressure sensor for a 90 grand am three pin, as advised from thirdgen.org forum. ACDelco part 15-72104. It is wired correctly and using my multimeter, I am getting correct voltage on all the PCM's ac wiring. The only thing in question right now is the Red/Black wire on the pressure switch C2 pin 14, circuit 380. I register 4.2v there, and I believe that is too high for it to turn the compressor on. I don't know what the observable range should be for this?

I start the car with the AC turned on, and the fans immediately come on, but I don't hear the AC compressor engage. I have taken the pressure sensor pigtail loose, and the fans immediately go off, and I am almost sure I hear the AC compressor click like its either engaging or disengaging.

I have ordered another pressure sensor to see if maybe I have a bad one, I have read 2-2.5 volts is where it should operate. My ac tech that filled it with R134 swears it is filled correctly and the system shouldn't be over pressure.

I still have the third gen cycling switch hooked up, but from studying the 02 LS1 AC wiring diagram its not even being used. Should I unplug this?

The PCM was programmed with HP Tuners as an 02 Camaro OS ID 12212156

Any help or advice appreciated.

Bryan

Lonnie P

Did you provide the LS1 F-body computer or did you get it from someone else?


The truck PCM's work for your engine but have different AC control. These are often provided as replacement computers.


I had to do a segment swap with the tuning software on the 411 truck PCM I had to get the AC to work properly.

bryanwood74

That actually makes a lot of sense now. I guess I'm off to buy hptuners pro. I bought the PCM (and it is a 411) from PSI conversions and I thought I got the right thing at the time. Had a friend do my tune with hptuners and he doesn't have his cable any more...

bryanwood74

Which segments did you have to swap?

Lonnie P

I got one from them also. It was from an 06 truck if I remember correctly.


Unfortunately I do not remember the details, but you can flash an entire F-body operating system onto the ECM. This will likely give you all the proper control for your swap.

bryanwood74

From the OS information etc in HP tuners it appears as an 02 fbody, and I know the tuner had to reflash it before he started on it. It even has the correct OS id for an 02 camaro. I don't want to loose my tune, but I will see if segment swapping will do the trick. I am in the process of buying the hpt pro now.

Lonnie P

If it is an 02 F-body operating system, then the segment should be already correct.


Look at the pressure reading with a scan tool to see if you get the proper pressure reading. Sounds like it is working correctly as the fans work.


Typically the sensor doesn't see enough pressure to activate the fans unless the compressor generates some pressure, or the engine compartment is very hot.


You can easily see the compressor turn when it engages. Did you verify it turns with the engine?


Keep in mind that the factory AC switch is tied through the low pressure switch to the compressor. The 411 pcm takes an input from the switch & sends an output to the compressor. Did you rewire these connections to get the signal to the PCM?

bryanwood74

Ok after fighting to get the ac to run, I think I have figured out part of the puzzle. What was I supposed to do with the cycling switch on the accumulator / drier? I think this is the culprit - at least looking like it.

I have it all wired correctly, I can command it on through hptuners and it runs fine. What I do notice is a status bit for "AC Pressure (Disable)" with status: disengaged(in red) when the cycling switch is plugged in and I command ac on.

When I unplug the cycling switch plug, it doesn't show this when I command the system on. Also it doesn't allow ac system request from the ac controls either. I feel like if I were to run a wire from the ac request from the controls straight to the computer it would probably engage the clutch like it should.

I know part of you harness connects to a factory connector where ac request is and could tap in there. What do you suggest?

Lonnie P

I used a relay directly off the switch to the ECM.
I also reused the factory wire from the AC switch by connecting it to the ECM (via another relay) & out to the AC clutch.

bryanwood74

All my issues were resolved by swapping the 5v and ground on the three pin connector for the high pressure sensor. Everything works as it should now. I am going to use an r134 switch on low pressure side so it will pass voltage through it from the ac switch. Just posting this for other folks future benefit in case anyone else runs into problems.