A/C Woes - Opinons/Guidance Welcomed

[atomic_hoji]

You swapped an engine, an HVAC issue can't defeat you!

The usual clause: I am also not an A/C expert - at all, by no means, lol.

But, a few observations.. Gauges are (generally) 1/2 the smallest subdivision for accuracy; quality, calibration, range (these are different range gauges) all effect gauge accuracy. To me, you have (basically) the same values LOW and HIGH pressure sides; it's equalized. I assume it is either the compressor hasn't run or it has a fault - an internal bypass or something is allowing pressure back through. Though in my experience with other types of compressor/pumps if a fault was the case you would see higher pressure on the HIGH side while it was running and it would equalize after shutdown.

When you have the engine running and the A/C on, are you sure that the A/C compressor clutch is energized and running the compressor? I ask because it may not run for one of the following possible reasons:

* A/C line pressure sensor detecting too low pressure, so A/C computer is cut-off A/C compressor run signal; i.e. not energizing the A/C clutch.
- A/C compressor or pressure sensor wire pins from engine harness to body harness are different (can't remember what you used for harness or if you checked the connections to the body differences or not..) so signal is not getting to the A/C compressor.
- A/C compressor or pressure sensor disconnected.
- usual suspects of poor connections or grounds.

I starred the first one as I have a hunch that may be the issue - this cut-off is how I keep my A/C system disabled at the moment since I haven't filled mine yet. The low pressure on the line sensor keeps the A/C clutch from energizing, or at least that's my recollection from months ago when I read up on it; those marbles have since been pushed out.. lol

If you hear it clunk, revs drop slightly, and A/C compressor pick-up then my point is probably moot. But if not, then maybe try the following check: disconnect the 2-wire connector at the A/C compressor, start the car, and select the A/C OFF. Check the SOL+ wire with a multimeter and see if it's powered. Do this again with the A/C ON and see if it's powered now. This should tell if the computer is requesting the A/C compressor to run.

-- Adam

[06YarisRS]

Originally Posted by atomic_hoji

You swapped an engine, an HVAC issue can't defeat you!

The usual clause: I am also not an A/C expert - at all, by no means, lol.

But, a few observations.. Gauges are (generally) 1/2 the smallest subdivision for accuracy; quality, calibration, range (these are different range gauges) all effect gauge accuracy. To me, you have (basically) the same values LOW and HIGH pressure sides; it's equalized. I assume it is either the compressor hasn't run or it has a fault - an internal bypass or something is allowing pressure back through. Though in my experience with other types of compressor/pumps if a fault was the case you would see higher pressure on the HIGH side while it was running and it would equalize after shutdown.

When you have the engine running and the A/C on, are you sure that the A/C compressor clutch is energized and running the compressor? I ask because it may not run for one of the following possible reasons:

* A/C line pressure sensor detecting too low pressure, so A/C computer is cut-off A/C compressor run signal; i.e. not energizing the A/C clutch.
- A/C compressor or pressure sensor wire pins from engine harness to body harness are different (can't remember what you used for harness or if you checked the connections to the body differences or not..) so signal is not getting to the A/C compressor.
- A/C compressor or pressure sensor disconnected.
- usual suspects of poor connections or grounds.

I starred the first one as I have a hunch that may be the issue - this cut-off is how I keep my A/C system disabled at the moment since I haven't filled mine yet. The low pressure on the line sensor keeps the A/C clutch from energizing, or at least that's my recollection from months ago when I read up on it; those marbles have since been pushed out.. lol

If you hear it clunk, revs drop slightly, and A/C compressor pick-up then my point is probably moot. But if not, then maybe try the following check: disconnect the 2-wire connector at the A/C compressor, start the car, and select the A/C OFF. Check the SOL+ wire with a multimeter and see if it's powered. Do this again with the A/C ON and see if it's powered now. This should tell if the computer is requesting the A/C compressor to run.

-- Adam

I think you're right Adam that the A/C compressor has not cycled at all. I listened intently for the sound of it engaging and the rpm drop and it never did either. I was thinking that there might be an electrical issue and had planned to look at the wiring diagrams. I did wonder if there were pin inconsistencies between the Yaris and xD harnesses but will have to look to see which side controls the A/C. Since I didn't download all diagrams, I may go back to TIS for another 2 day membership and see if I can sort it. In the meantime, I thought about manually cycling the clutch with a 12V battery - out of my lawn tractor - to see if can get the compressor running and observe the gauge readings.

To your starred point about low pressure, when I started with my first can of R134, it was leaking out of the fittings. Maybe I just didn't get enough in there, but at the same time, I'd think 50 psi in the low side would be enough to trigger the compressor. That said, in the ChrisFix video, when he added R134, the pressure on the low side shot up way past my 50 psi.

I am going to start with your recommendation about testing the connector with a multimeter. I'll report back with my findings.

Thanks a ton, Adam

[atomic_hoji]

Originally Posted by 06YarisRS

I think you're right Adam that the A/C compressor has not cycled at all. I listened intently for the sound of it engaging and the rpm drop and it never did either. I was thinking that there might be an electrical issue and had planned to look at the wiring diagrams. I did wonder if there were pin inconsistencies between the Yaris and xD harnesses but will have to look to see which side controls the A/C. Since I didn't download all diagrams, I may go back to TIS for another 2 day membership and see if I can sort it. In the meantime, I thought about manually cycling the clutch with a 12V battery - out of my lawn tractor - to see if can get the compressor running and observe the gauge readings.

To your starred point about low pressure, when I started with my first can of R134, it was leaking out of the fittings. Maybe I just didn't get enough in there, but at the same time, I'd think 50 psi in the low side would be enough to trigger the compressor. That said, in the ChrisFix video, when he added R134, the pressure on the low side shot up way past my 50 psi.

I am going to start with your recommendation about testing the connector with a multimeter. I'll report back with my findings.

Thanks a ton, Adam

While I was out installing my flow straightener in the intake this afternoon I double checked and my A/C line pressure sensor is on the HIGH side of the A/C system. That was my recollection and why I thought 50 psi might be too low. That being said, I believe you can overcharge a system too, so possible something is telling it there's too much in the system and giving it a cut-off. Do you have any OBD2 code thrown? I checked mine and I have no (A/C related! lol) codes being thrown, but the A/C cut-off is ON as I anticipated given I haven't charged my system.

If you find it is not getting a signal to energize the A/C solenoid and run the compressor that will at least tell you something is tripping it up. Giving it a nudge with a 12V external supply is a clever idea! I would just caution that you give it a brief bump and see what the pressures do - if the A/C system is giving you a cut-off, it's for a reason.

Did you make any changes on the connector that goes is a part of the engine harness that runs up to the main junction box in the engine bay? That's the connector that the wire for the A/C compressor runs from the engine side to the body side of the vehicle, and then on to the A/C computer. That'd be my starting place to look for wire harness differences.

Keep us posted!
-- Adam