AC Cycling

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doru said:
Give us the screenshot after the compressor shuts off. Pay attention at "Number of Trouble Codes". It might change to 1. Intermitent failures may create intermitent codes. If "Number of Trouble Codes" changes, make sure you go to the Trouble Codes and see what that code is.
Click to expand...
Ran it for 10 mins or so with live data going and no intermittent codes showed up.

However, something is going on with the rear AC.
The 3rd row upper and lower vents are not cooling at all. Just blowing warm air. When I turn the rear AC on (it doesn't seem to come on by hitting AUTO on the front), the compressor is staying on a lot longer.
But the AC is not cooling. In fact when the rear is running, I am getting barely cold air in the front. With the rear off, cooler air comes out the front but of course compressor goes off within 8-10 secs.

the estimated rear temps are just not making any sense. i am wondering if the rear AC controls are not working properly.
here's screenshots with compressor OFF and and also Rear ON.
1777927995323.webp


compressor off.webp


rear on.webp
 
GrouchyTech said:
I’d like to see a refrigerant recovery to see how much is in there… I think you’re undercharged
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that's what I need to eliminate. Taking it back to Clear Choice Lexus place either tomm or next week.

i wonder if this is what I am hearing from the front controls area.
unclemat

Thread 'Hissing noise from A/C expansion valve'

So a MY15 200 I bought 2 weeks ago had a faint but noticeable periodic hissing from the dash in the cluster area. I narrowed it down to A/C, and based on my googling everything pointed at the expansion valve and the refrigerant being tad low.

I took her in yesterday to the dealer I bought from and asked them to evacuate and recharge the system. Problem solved. They told me it was within range, just on the lower end of it.

Just putting it on there in case somebody has or will have a similar issue. The noise was low, many probably would have ignored it, and even I missed it during the test...
 
Sajan said:
that's what I need to eliminate. Taking it back to Clear Choice Lexus place either tomm or next week.

i wonder if this is what I am hearing from the front controls area.
unclemat

Thread 'Hissing noise from A/C expansion valve'

So a MY15 200 I bought 2 weeks ago had a faint but noticeable periodic hissing from the dash in the cluster area. I narrowed it down to A/C, and based on my googling everything pointed at the expansion valve and the refrigerant being tad low.

I took her in yesterday to the dealer I bought from and asked them to evacuate and recharge the system. Problem solved. They told me it was within range, just on the lower end of it.

Just putting it on there in case somebody has or will have a similar issue. The noise was low, many probably would have ignored it, and even I missed it during the test...
Click to expand...
That’s why I originally asked “Can you hear the refrigerant behind the dash when it’s cycling? Kind of a hissing+liquid sound.”
 
GrouchyTech said:
That’s why I originally asked “Can you hear the refrigerant behind the dash when it’s cycling? Kind of a hissing+liquid sound.”
Click to expand...
Yep, it’s definitely a hissing sound, initially I thought it was some kind of fan spinning up. I think I mentioned that in one of the earlier post.
 
GrouchyTech said:
The low volume causes the vapor to mix with the liquid, which then flows through the valve. It’s supposed to be liquid through that valve, no gas.
Click to expand...
Took it back to Clear Choice. They hooked up the machine and did an evacuate/recharge.
Service advisor said i was below 1.75 and max is 2.13?
i am assuming he meant lbs..
1.75 = 28oz
2.13 = 34.2oz

Some quick googling...I think w/o a cool box the specs are
32.5 ± 1.1 oz. or 1.96lbs to 2.1lbs.

They refilled it and then left it on and it held pressure.
The back vents are blowing colder air now.
 
So the issue is still there. Something just doesn't make sense.

If I turn off the rear AC, the front temps are ice cold...45 F..
problem: it cycles frequently. 8-10 seconds. I notice it because the RPM goes from 650 to 800 and back down.

with the rear ON, front vent temp goes up slightly...maybe 48-50F. Still cold, and AC stays on longer trying to cool the rear.
additional problem: rear is not cooling as much.

Vent temp at the 2nd row upper and middle vents are 56-57 F and air flow feels lower than the 3rd row vents which I can really hear also.
3rd row vents are cooler than the 2nd row. they are at 52 F.

I left the car on idling for 10+ mins and took a picture of the techstream readings. I was sitting in the back seat and I was "comfortable", certainly not 70F but not warm either.

Room temp in the front at 77.45 F
Room temp in the rear at 91.85 F
Estimated rear temp at 23.99F (normal readings are supposed to be: 63 - 90 aka actual set temp)
Foot duct sensor showing 97 F

I am lost.
 
Last edited:
Hi Sajan,
Ive been troubleshooting my ac, once hot, the ac would continuously engage/disengage. The ac light would blink accordingly and
My magnetic clutch shims needed to be adjusted after years of wear on clutch surface.
 
camino70 said:
Hi Sajan,
Ive been troubleshooting my ac, once hot, the ac would continuously engage/disengage. The ac light would blink accordingly and
My magnetic clutch shims needed to be adjusted after years of wear on clutch surface.
Click to expand...
Interesting. Did it throw any codes?

The other thing I can think of is something to do with the rear expansion valve or something is blocked? I am not well-versed on AC symptoms...
 
long shot, but do you have the "climate concierge" enabled? It might interfere with some of these readings and cycles, since it keeps balancing the temperature around the cabin.
 
MRego said:
long shot, but do you have the "climate concierge" enabled? It might interfere with some of these readings and cycles, since it keeps balancing the temperature around the cabin.
Click to expand...
I noticed it cycling without climate concierge also.

At this point I am ready to take it to the dealer because these independent folks just do the typical checks of pressure and say all is good.
 
after totally wasting hours chasing this, I believe this is normal behavior once the car reaches set temp in the cabin and fan speed is down to 1-2. I asked someone else with a LX 570 same year, and also just compared it to a stranger's 2019 LX. Both behave the same way. 8-10 secs seems short but it's normal for this truck once the heat load is very low.
Also the random readings from the estimated temp PIDs is normal. @GrouchyTech confirmed his truck shows random numbers also.

I had taken it to the dealer a few days ago who had to evacuate and refill the refrigerant to the right levels (added dye) because Clear choice "overfilled it". dealer didn't tell me how much it was overfilled by and what the amount they filled it to. i asked the service advisor but he said the tech didn't tell him. grr...
While I was there I also got the AC ECU reprogrammed to the lasted version to address the servo motor TSB. the dealer also reinitialized the servo motors which fixed the rear blower running high.

my wife is disappointed in me for trying to make something out of nothing haha..
i mean, there was something...at least the servo stuff had to be addressed.

I will keep monitoring it but this was a good learning experience of AC systems.
 
Odd observation, but worth a shot since it’s free, and this may sound silly, but try it…

On my 2010 LC variant, the AC was doing very weird things when I first got it, very similar to what you’re describing

After some digging, I found an auto AC setting in the nav menu, shut that off and has been running fine/normal ever since.

Never really looked into why it was causing weird behavior; but it stopped it

Worth a try since it’s free.99

IMG_2963.webp
 
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