A/C Woes - Opinons/Guidance Welcomed - Toyota Yaris Forums

atomic_hoji · 12-08-2018, 10:17 AM

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

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12-08-2018, 10:17 AM	#4
atomic_hoji Drives: 2018 Yaris SE 5MT Join Date: Aug 2017 Location: Kincardine, ON, Canada Posts: 273	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