AC Cycling

[Sajan]

It's mid 80s F outside, I have the AC on auto at 74 F.

I noticed the AC cycles very frequently.
It goes from cold air to lukewarm air ...a lot. I can hear it come off and on ..like every 30 secs.
Is this normal for these trucks? Are there any diagnostics I can perform using techstream?

I had something like this in my 5 series back in 2020 and they ended up replacing the AC compressor under warranty I think

EDIT: 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.

 

[Sandroad]

Not normal for my ‘17. How’s your refrigerant charge?

 

[elcie200]

It's mid 80s F outside, I have the AC on auto at 74 F.

I noticed the AC cycles very frequently.
It goes from cold air to lukewarm air ...a lot. I can hear it come off and on ..like every 30 secs.
Is this normal for these trucks? Are there any diagnostics I can perform using techstream?

I had something like this in my 5 series back in 2020 and they ended up replacing the AC compressor under warranty I think

I had the same recently. Was the ac compressor. Or as I like to call it the “ac compre$$or” lol

My shop looked at the relay and switch, refrigerant charge, ac pulley, then compressor. Found metal bits on the outside (not inside). Iirc if there’s metal bits “inside” the fix is much more involved/expensive.

 

[Sajan]

Not normal for my ‘17. How’s your refrigerant charge?

definitely not normal. the compressor is only staying on for about 8 secs before cycling off. something is causing it to turn off.

my pressure...depending on if the AC was running or not..
low side was going between 30 to 50 (30 when on, 50 when off)
high side was around 200-250. .

Normal readings (I believe when compressor is running):

• Low 21 to 36 psi
• High 199 to 228 psi

 

[GrouchyTech]

Do you have Techstream or some way to read PID values and DTCs?

Have you had any work done on the A/C— EVER? What about any other work that could have required a refrigerant evacuation/recharge?

Can you hear the refrigerant behind the dash when it’s cycling? Kind of a hissing+liquid sound.

Is your condenser fan operating? It won’t turn all the time (even when the compressor is operating), but the engine is warm and idling in park at 85°F ambient it should be operating and moving a good amount of air.

The LC200 doesn’t really have an issue with rock damage to the condenser (that I’ve noticed) because of its location, but I’d do a quick check of the condenser just to be sure. Maybe it has damage or has debris blocking airflow.

Get a flashlight and open the hood to check the front of the condenser. Look very closely at the thin horizontal “plates” (coils) for rock damage, which will look like a little dent with a pinhole or a crease. Look for dark/dirty spots which indicates oil seeping out of the damaged area.

 

[Sajan]

Yes I have access to techstream. Anything in particular I should look for?

No work on AC from on my part and I didn't see anything from the PO in the invoices.
However they worked in that area for the supercharger/aftermarket bumper install so it's possible something happened then.

Fan appears to be running. Will double check again tomm.

Big condenser...I am looking through some of the old pics the PO sent me, I do see a large dark spot..

This is from 2022:

 

[GrouchyTech]

Do the following as best as you can and get a video of what you see in the sight glass on the high side.

• Temperature at the air inlet is 30 to 35°C (86 to 95°F).
• Engine is running at 1500 rpm.
• Blower speed control switch is at HI.
• A/C switch is on.
• Temperature control switch is at the MAX. COOL position.
• Fully open doors

Also, post a screenshot of your A/C data list with engine off/cool. And then with engine on/hot and A/C OFF, and then engine on/hot with A/C ON.

 

[Sajan]

Do the following as best as you can and get a video of what you see in the sight glass on the high side.

• Temperature at the air inlet is 30 to 35°C (86 to 95°F).
• Engine is running at 1500 rpm.
• Blower speed control switch is at HI.
• A/C switch is on.
• Temperature control switch is at the MAX. COOL position.
• Fully open doors

Also, post a screenshot of your A/C data list with engine off/cool. And then with engine on/hot and A/C OFF, and then engine on/hot with A/C ON.

I will try to get you that sometime today or tomorrow.
I also booked a service appointment with clear choice Houston.

Only dtc was one lost communication with navigation ECU.

Here’s a screenshot of Techstream live data with the AC running full blast

 

[Sajan]

clear choice texas, they found nothing wrong. they said they saw the code and think that's why it's going into a loop..

U0163 Lost Communication With Navigation ECU

DTC Detection Condition
No communication with multi-media module receiver assembly

Trouble Area
CAN communication system
Multi-media module receiver assembly
Air conditioning amplifier assembly

I wonder if it was because of me flashing the ECU with a tune and not clearing all the codes? Maybe it was stuck in service mode?
Either way gonna go pick up the car and see if it's still doing it.

 

[Sajan]

Ok still the same behavior. Maybe it’s normal?
At 88 F outside, and Ac on 74 auto, it blows cold air for about 8-10 secs , then off for 13-15, then on for 10 secs..

So odd.

 

[Mingus Dew]

Ok still the same behavior. Maybe it’s normal?
At 88 F outside, and Ac on 74 auto, it blows cold air for about 8-10 secs , then off for 13-15, then on for 10 secs..

So odd.

Don’t think it’s normal. My AC is on 74 pretty much constantly and it’s about that temp here right now and I get a steady stream of cold air.

Only time I’ve ever experienced “warm” (or really just not cold) air while the AC was engaged was when I had it set to 76 and it was about that temp outside. Put it down to 74 and it was cold again.

Maybe a dumb question, but have you tried setting it to something ice cold like 68 to see if the same thing happens?

 

[Sajan]

Don’t think it’s normal. My AC is on 74 pretty much constantly and it’s about that temp here right now and I get a steady stream of cold air.

Only time I’ve ever experienced “warm” (or really just not cold) air while the AC was engaged was when I had it set to 76 and it was about that temp outside. Put it down to 74 and it was cold again.

Maybe a dumb question, but have you tried setting it to something ice cold like 68 to see if the same thing happens?

I set it to like 70 and it stayed on for a 5-10 secs more.
I am waiting till it hits 90+ here to truly test it out. We had another "cold front" that brought it down to the 60s haha

I don't think it's normal either...but this is also my first Toyota with an Auto mode...

 

[Mingus Dew]

I set it to like 70 and it stayed on for a 5-10 secs more.
I am waiting till it hits 90+ here to truly test it out. We had another "cold front" that brought it down to the 60s haha

I don't think it's normal either...but this is also my first Toyota with an Auto mode...

I know nothing about automotive AC but living in Florida you need to have a bit of general AC knowledge to survive.

It sounds like your compressor is short cycling which is odd. It's reaching internal temp (or it thinks it is) and then shutting off before starting again when the temp rises. On a central unit this often happens when the system is oversized for the space it's meant to cool. Obviously that's not possible here.

I would think that the Auto setting would regulate fan speed and other functions such that the AC stays on constantly rather than short cycling, which is what my Auto setting does.

 

[Sajan]

I agree. The two times this happened to me, both times something was wrong.

1. bmw 530i, i felt the same warm air every so often and they ended up relacing the compressor under warranty.
2. my house upstairs AC, compressor wouldn't stay on for more than 10 secs and it turned out my evaporator coil had a leak.
according to the mechanics, they see nothing wrong..


Am I supposed to get readings from these two sensors?

 

[Mingus Dew]

I agree. The two times this happened to me, both times something was wrong.

1. bmw 530i, i felt the same warm air every so often and they ended up relacing the compressor under warranty.
2. my house upstairs AC, compressor wouldn't stay on for more than 10 secs and it turned out my evaporator coil had a leak.
according to the mechanics, they see nothing wrong..


Am I supposed to get readings from these two sensors?

View attachment 4132947

Can't speak to the sensors. Someone more knowledgeable will need to respond.

I would imagine that your mechanic would have found a coil leak as those are pretty easy to diag.

 

[TomEf]

That short of a compressor cycle sounds a lot like a low refrigerant condition tripping a safety shutoff for the compressor. Went through that with a different truck last year.

 

[GrouchyTech]

There are just too many possibilities to pin anything down here. Low refrigerant, moisture freezing in the system (would have showed up much sooner), A/C amplifier, compressor, Nav/display unit, A/C controls (the buttons), etc.

Does it EVER operate longer than a few seconds at a time? Such as, when the engine is cold does it operate pretty normally for a period of time and then start acting up?

 

[Sajan]

There are just too many possibilities to pin anything down here. Low refrigerant, moisture freezing in the system (would have showed up much sooner), A/C amplifier, compressor, Nav/display unit, A/C controls (the buttons), etc.

Does it EVER operate longer than a few seconds at a time? Such as, when the engine is cold does it operate pretty normally for a period of time and then start acting up?

I put it on LO. opened the doors..and I can hear and see the compressor+fan kick on, stays on 8-10 secs, shuts off.
So it doesn't seem to be affected by how much it needs to cool down. It's not letting the compressor or fan stay on for too long.
I can also see a change in RPM.
Near the AC controls, I can hear it hissing or some sort of fan when the compressor kicks on, cool air flows and bam, turns off.

Really trying to avoid a trip to the dealer...

 

[Sajan]

I was messing around with the various controls and it seems like the rear AC controls are not behaving or syncing properly. Not sure if this is normal behavior though. Need to double check with another LX 570 and see..

When I turn off 4-zone, the temperatures sync up. Then I turn the AC off and only the front goes off..I still hear the rear fans blowing. Then when I go back to the rear controls (between the seat) and set it to OFF, it turns off.
When I hit Auto in the front, the rear AC is not coming back on.

These two values are supposed to be 63.5 to 90.5

What part is the Cooler control switch sub-assembly system??

 

[doru]

I also booked a service appointment with clear choice Houston.

Only dtc was one lost communication with navigation ECU.

Here’s a screenshot of Techstream live data with the AC running full blast

View attachment 4130251

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.