Reat seats AC - Model X

[Enz295]

Quick question:
With the "rear AC menu" showing AC off, fan speed greyed out at 0, and nobody seating in the back (6 seater) I have 2 questions:
-is the rear central vent supposed to blow air at all?
-if yes, is the back AC supposed to stay off, even though the front AC is on (nobody in the back)?
Thx

 

[dogldogl]

Both of the scenarios you describe are expected/normal.

-is the rear central vent supposed to blow air at all?

Even if the rear AC compressor / heat-exchanger is inactive, the vents at the rear of the front center console (ie. center vents for 2nd row) will mirror whatever climate (fan speed/temperature) is enabled for the front row. (in a 6 or 7 seater, there are two separate AC units, One for the front row & center of 2nd row, and one for everything else - you'll see the fluid volume of each unit on a sticker near the frunk cavity)

-if yes, is the back AC supposed to stay off, even though the front AC is on (nobody in the back)?

Yes. If you have a 6 or 7 seater, you also have a separate rear AC unit. It is only active (automatically if full AUTO selected for rear) if occupants are detected in the 2nd or 3rd row(s) & you simultaneously have vehicle climate powered on.

The rear AC can also be manually activated of course.

 

[Big Earl]

As mentioned above, the vents in the back of the front center console (between the front seats) are connected to the front HVAC system.

 

[AnxietyRanger]

Even if the rear AC compressor / heat-exchanger is inactive

We (some members on TMC) have researched this extensively and believe the rear unit is only a fan (and temperature-adjusting valves).

It was discussed extensively e.g. here: A/C Effectiveness in 5-seat configuration - Predictions?

There is only one compressor in all of them: 5/6/7 seaters. 6/7 seaters adds rear fan, driving rear (side?) vents and the added extra vents in the third row (the fan assembly is on the right side of trunk).

Otherwise your message is of course spot on.

 

[dogldogl]

I'm going to veer moderately off-topic for a moment (sorry OP).

...and believe the rear unit is only a fan (and temperature-adjusting valves).

Thanks for the thread link @AnxietyRanger, in which @essmd proposes a hypothesis (repeatedly) that the AC is the same in 5/6/7 seat configurations and then asserts a bunch of dependencies predicated on this assumption.

It's an interesting hypothesis. I have an alternate.

View media item 117879980g of refrigerant in the DUAL HVAC configuration (6/7 seater)
720g of refrigerant in the SINGLE HVAC configuration (5 seater)

230g compressor oil in the DUAL configuration
140g compressor oil in the SINGLE configuration

The high voltage lines to a substantial additional hardware component, present only on the 6/7 seater & substantially larger volume of refrigerant & compressor oil kinda "occams razor" toward the contrary. Whether or not there are two compressors or one* wouldn't contradict an expectation that the 6/7 seat configuration (DUAL HVAC) might be expected to cool/heat the cabin interior at an increased rate/capacity compared to the 5 seater (SINGLE HVAC).

*I admit I don't have proof either way. I mean no malice & am interested to learn.
Given the AC consumes a substantial quantity of power, it might be a worthy experiment to run the front vs front+rear AC while charger is attached (the current can be measured via IC or app during this operation).

 

[Big Earl]

The single HVAC system (5 seat X) has one compressor, two evaporators (one for battery cooling and one in the dash) and one PTC heating element (6 kW in the dash).

The dual HVAC system (6 and 7 seat X) has one compressor, three evaporators (one for battery cooling, one in the dash plus a smaller one in the rear) and two PTC heating elements (6 kW in the dash and 2.5 kW in the rear).

The extra refrigerant required for the dual unit is due to the extra evaporator and the refrigeration lines that run from the front of the vehicle to the rear of the vehicle. The system does not have two compressors.

 

[AnxietyRanger]

@dogldogl @Big Earl Great new insights, thank you. The additional info on compressor oils on 6/7 seaters is good info.

We did note the high voltage lines running to the rear fan, but at the time we did not at the time find any information about evaporators or extra refrigerant lines, and Service Centers spoke of the rear fan assembly only.

We did speculate about additional heating being part of the rear fan assembly, and @Big Earl seems to confirm that now.

Overall it seems that in addition to additional fan power, the 6/7 seaters do have some additional cooling and heating power, though there is only one compressor.

For those looking for the past research, e.g. this page: A/C Effectiveness in 5-seat configuration - Predictions? #41 onwards

 

[mattack4000]

While we are on the topic, do you guys find the fan in the back to be loud above 3? It seems like in the auto setting, the fan likes to be at about 4. I just find the fan noise to be extremely loud. Do you guys feel the same? 3 and below are fine

 

[Big Earl]

While we are on the topic, do you guys find the fan in the back to be loud above 3? It seems like in the auto setting, the fan likes to be at about 4. I just find the fan noise to be extremely loud. Do you guys feel the same? 3 and below are fine

It's definitely noisy above setting 3. Fortunately, higher settings don't really increase the system's effectiveness, so there's really no need to go above fan speed 3.

 

[mattack4000]

The auto srtting keeps putting it to 4 or 5!

 

[essmd]

It is a special feeling to initiate a question (in doubt of what Tesla Reps claim) and starting a thread that has quite a good following and duration, follow up with hands-on researched evidence (,then to be quoted and quasi-criticized for the hypothesis by seemingly intelligent peers...

I'm going to veer moderately off-topic for a moment (sorry OP).

Thanks for the thread link @AnxietyRanger, in which [USER=38377]@essmd[/USER] proposes a hypothesis (repeatedly) that the AC is the same in 5/6/7 seat configurations and then asserts a bunch of dependencies predicated on this assumption....

.. Then to affirmed to be correct by others

The system does not have two compressors.

...Then again to have original thread and posted research cited...

@dogldogl @Big Earl Great new insights, thank you. The additional info on compressor oils on 6/7 seaters is good info.

For those looking for the past research, e.g. this page: A/C Effectiveness in 5-seat configuration - Predictions? #41 onwards

Tesla owners all have one thing in common, although some realize this more than others, that future and current owners are all subject to the desired technical information that is held tightly by Tesla, and rely upon our peers to research and provide the truth... eventually...

I know there are many 5-seater owners that would have preferred to know up front that the cooling effectiveness behind the first row was definitively compromised, although utilizing the the same size A/C compressor as the other seating configs but only a single fan motor to circulate cooled air. This was a significant realization made after delivery, mostly impacting those living in climates with hot summers. And accordingly we are not surprised that Tesla does not offer any response to this.

Also, had there been any advanced announcement of the future ability to fold down the second row in the 7-seat config (as the very first Model X was demonstrated by Elon), many would have willingly waited for and paid the extra cost for that design, with extra seating and 2 circulating fans.

But so is the life of the Tesla enthusiasts/owner, similar to that of a mushroom (kept in a dark environment, constantly fed Bulls**t)... yes Woe is Us and our high vehicle investments enjoying many aspects.

Just when will those of us with HW 2.0 get that Enhanced Autopilot, or those who that paid $3k for Full Self Driving see that fulfilled... or refunded???... But I digress.... sorry

Much needed rant over...

 

[scottf200]

We (some members on TMC) have researched this extensively and believe the rear unit is only a fan (and temperature-adjusting valves).

It was discussed extensively e.g. here: A/C Effectiveness in 5-seat configuration - Predictions?

There is only one compressor in all of them: 5/6/7 seaters. 6/7 seaters adds rear fan, driving rear (side?) vents and the added extra vents in the third row (the fan assembly is on the right side of trunk).

Otherwise your message is of course spot on.

It is interesting that the diagnostics screen on my 6 seater X show 2 HVACs (Aux HVAC being the 2nd) but only 1 'Refrigernet Loop' section.
Diagnostic screen = 2021.24.4 - dynotest -- mentioned in various threads. ie. Model Y 82kW Battery Pack

 

[Big Earl]

It is interesting that the diagnostics screen on my 6 seater X show 2 HVACs (Aux HVAC being the 2nd) but only 1 'Refrigernet Loop' section.
Diagnostic screen = 2021.24.4 - dynotest -- mentioned in various threads. ie. Model Y 82kW Battery Pack

It’s one loop with two evaporators that are each activated via solenoids (very top of your pic). The refrigerant loop section covers the pressures entering (suction) and leaving (discharge) the compressor.

 

[brainhouston]

anyone know where the sticker is with Freon type and amounts? i can't seem to find it...

 

[scottf200]

anyone know where the sticker is with Freon type and amounts? i can't seem to find it...

free service manual - Tesla's Service Manuals Now Free Of Charge, Grab Them While You Can

 

[brainhouston]

free service manual - Tesla's Service Manuals Now Free Of Charge, Grab Them While You Can

nothing in there says where the sticker is or should be... maybe i overlooked but i can't find it...

 

[brainhouston]

found where it should be in parts catalog