MX Rear Heat Performance

[polymathic]

Picked my MX from the SC today... the diagnosis was that the rear vent work. It just takes forever for them to heat up. Recommendation was that let everything on auto and wait, wait, wait.... Not impressed.

 

[travwill]

Picked my MX from the SC today... the diagnosis was that the rear vent work. It just takes forever for them to heat up. Recommendation was that let everything on auto and wait, wait, wait.... Not impressed.

Agree, same here was told. I would say, if turning on the rear heat, keep everything on auto except the temp. Turn that up to HI. Fan speed will stay at 2 for quite a while, then creep up after a while.

 

[polymathic]

Agree, same here was told. I would say, if turning on the rear heat, keep everything on auto except the temp. Turn that up to HI. Fan speed will stay at 2 for quite a while, then creep up after a while.

Good advice. Setting rear heat temp to high, but keeping fan to auto, got things to warm up reasonably fast.

 

[FURY]

Will try to sum it up. All Xs have vents under the front seats, that blow forward to heat the cabin (not rear). The middle console vents though do blow backwards.

The 5 seater depends on all of this only, mainly heat from center console going back.

The 6/7 seater do not have any vents in 2nd/3rd row on floor, just two in the side pillar in 2nd row, and two in side pillar in 3rd row. The A/C works pretty well from these vents I recall in hot Summer. The heat though doesn't. It does take a long while to warm the air up, and it is never as warm as the front air. But, in really cold weather, after quite a while, it does reach a temp that would warm up the cabin or help as its warmer than outside for sure. Maybe it gets up into the 70s max I've felt.

Has anyone have info on enabling/reducting/other the pillar ducts that function on the 6 & 7 seat X configurations, for 5 seaters ? Pets and other rear seat occupants would likely benefit, at some point, from the airflow output, especially with warmer ambient temperatures.

Thank you very much

Fury

 

[travwill]

Has anyone have info on enabling/reducting/other the pillar ducts that function on the 6 & 7 seat X configurations, for 5 seaters ? Pets and other rear seat occupants would likely benefit, at some point, from the airflow output, especially with warmer ambient temperatures.

Thank you very much

Fury

From the pics I saw, the ducts and vents are not in the 5 seaters. Did you see some with them?

 

[FURY]

Hi Travwill!

I ordered up a five seater, AFTER I had the sales manager in my local SC sit in the five seater they had just received a few days ago, turn on the HVAC and confirm that the B pillars had functional ducting to send air to the rear seats. He also confirmed there was NO ducting, as the 6&7 seat configurations provide. He said that he would ask for the rear ducting to be reincorporated in builds, going forward. I reviewed with him that living cargo (i.e., dogs) may be placed in that rear section of a 5 seater and air flow, at the least would seem advisable. Not sure how a regulatory body would view a trip through the summer desert, in SW U.S., with a large breed dog in the way back of an X...

Nevertheless, I did add the rear seat heater option, as the HVAC system in TESLAS is not robust enough, for me. Cooling is another issue, of course and I passed on the seat ventilator another upgrade option-just not functional enough as TESLA provides at present.

BTW, I also asked the Sales Manager to enquire as to retrofitting rear compartment ducting, if my build can't be factory adjusted to do so. Also, the controls in the X he tested for me, did not allow selective control of HVAC zones, which is different, he said than the 6&7 HVAC control system.

I shall update as develpoments warrant.

Thank you very much

Fury

 

[Aljohn]

For those with 6/7 seat configs.... I placed the Climate to Auto for fan and temperature then moved to the second row seat while garage was cold enough. I raised the temp setting to 75 degrees to demand heat (I did NOT change the Fan setting to manual, it remained on AUTO). Initially, the rear heat was off (no passenger detected before I moved to the back and closed the FWD). In the heat mode, the center console vents turn OFF and the heat transfers to center vents under the front seat floor. The center pillars have some air circulating, but the heat from the 3rd row pillars is on and blowing warm air in a few minutes.

For those wondering, I didn't increase the Fan speed to a manual setting assuming if I set the temperature to demand heat, the Model X would warm the air to a temperature and volume that would efficiently raise the cabin to my setting (AUTO Setting algorithms). Adjusting the fan to a higher setting may cause to blower to increase through the vents making the air feel colder (same amount of warming, but forcing more air through the electric heat wires = cooler feeling air), or even overriding the heater's capacity to warm a significant greater volume of cold air per minute crossing the heater elements.

Thus I will continue to use Auto settings and adjust the temperature settings allowing the Model X to find the most efficient means to warm the cabin. Once the cabin warmed, I reduced the temp to my normal setting of 70 degrees. No issues here, but have to admit my cold extremes may not be as severe as others.

 

[Solarman004]

For those with 6/7 seat configs.... I placed the Climate to Auto for fan and temperature then moved to the second row seat while garage was cold enough. I raised the temp setting to 75 degrees to demand heat (I did NOT change the Fan setting to manual, it remained on AUTO). Initially, the rear heat was off (no passenger detected before I moved to the back and closed the FWD). In the heat mode, the center console vents turn OFF and the heat transfers to center vents under the front seat floor. The center pillars have some air circulating, but the heat from the 3rd row pillars is on and blowing warm air in a few minutes.

For those wondering, I didn't increase the Fan speed to a manual setting assuming if I set the temperature to demand heat, the Model X would warm the air to a temperature and volume that would efficiently raise the cabin to my setting (AUTO Setting algorithms). Adjusting the fan to a higher setting may cause to blower to increase through the vents making the air feel colder (same amount of warming, but forcing more air through the electric heat wires = cooler feeling air), or even overriding the heater's capacity to warm a significant greater volume of cold air per minute crossing the heater elements.

Thus I will continue to use Auto settings and adjust the temperature settings allowing the Model X to find the most efficient means to warm the cabin. Once the cabin warmed, I reduced the temp to my normal setting of 70 degrees. No issues here, but have to admit my cold extremes may not be as severe as others.

Thanks for the great update.
I had tried the technique of testing with a rear passenger a few weeks ago, but only in manual mode, and could not get hot air. I'll try again in Auto.
Were you able to get any hot air in the rear in Manual Mode?

 

[Aljohn]

Thanks for the great update.
I had tried the technique of testing with a rear passenger a few weeks ago, but only in manual mode, and could not get hot air. I'll try again in Auto.
Were you able to get any hot air in the rear in Manual Mode?

I didn't try manual fan mode for the reasons stated. If one "cranks" the fan's air flow, whether an electric car or ICE (hot water), unless there is a corresponding increase in the heat available, the air will eventually overcome the heat ex-changer. I would simply suggest using the temperature setting to force an increased fan speed with corresponding heat source. The down-side, and potentially the reason the X doesn't supply extreme heat source is its detriment to battery range (Tesla decrease the estimated range on 90D S by 50 miles if heat is operating at 32 degrees outside). Therefore the point is one must do BOTH -- increase the upward temperature along with the fan speed .... watch the battery use increase.

 

[travwill]

Hi Travwill!

I ordered up a five seater, AFTER I had the sales manager in my local SC sit in the five seater they had just received a few days ago, turn on the HVAC and confirm that the B pillars had functional ducting to send air to the rear seats. He also confirmed there was NO ducting, as the 6&7 seat configurations provide. He said that he would ask for the rear ducting to be reincorporated in builds, going forward. I reviewed with him that living cargo (i.e., dogs) may be placed in that rear section of a 5 seater and air flow, at the least would seem advisable. Not sure how a regulatory body would view a trip through the summer desert, in SW U.S., with a large breed dog in the way back of an X...

Nevertheless, I did add the rear seat heater option, as the HVAC system in TESLAS is not robust enough, for me. Cooling is another issue, of course and I passed on the seat ventilator another upgrade option-just not functional enough as TESLA provides at present.

BTW, I also asked the Sales Manager to enquire as to retrofitting rear compartment ducting, if my build can't be factory adjusted to do so. Also, the controls in the X he tested for me, did not allow selective control of HVAC zones, which is different, he said than the 6&7 HVAC control system.

I shall update as develpoments warrant.

Thank you very much

Fury

Ah thanks for the update. Will be interesting to see if they do some of this custom build work at times. For us, the rear A/C was critical this Summer on a roadtrip or two with our dogs in the back. There were times I had my temp at say 75 and was good, but the dogs were panting in the back unless I had their air on like 68 or so the whole time to blow more. If you have dogs as well I would say definitely get the rear sunshade as it makes a huge difference.

Enjoy!

 

[Solarman004]

I was motivated by the -5 deg F temperatures and snow today to finally test the rear compartment heating (cabin heat, not seat heaters). In the front, with the temperature set to 65 deg, after a minute I'm getting toasty hot air from the vents. But in the rear, with the temperature set to 79 degrees and fan on 7 or 8, after 5 minutes I'm getting cool to mildly warm air through the 2nd and 3rd row air vents.
So before I schedule a service appointment, I thought I'd ask if others are seeing the same heater performance and is this normal for the MX?
Thanks.

UPDATE: I finally had my service appointment and their conclusion was that nothing is wrong with my rear heater.
They recommended starting off rear heat on "Hi" then backing off the temp as the cabin heats. They told me that it was normal when both front and rear were set the same (72 deg, fan 3 for example) that the front air feels hot, but the rear feels cool.
When using Hi temp setting for the rear, after a minute or so, I could feel warm air-- at about the same temp as the front with 68 deg set.
A quick check of running the rear heater in Hi, with fan=3, and outside temp 55, showed an initial consumption of 2430 watts, gradually ramping down over 7 minutes to 1215 watts and stabilizing. At the lower level, on a long trip, I would lose 3.8 miles of rated range every hour.
My conclusion: try to use just seat warmers and front heater if possible. If that isn't enough, the rear heater consumption is not a show stopper unless I am cutting it close on range remaining at destination.

 

[hiroshiy]

UPDATE: I finally had my service appointment and their conclusion was that nothing is wrong with my rear heater.
They recommended starting off rear heat on "Hi" then backing off the temp as the cabin heats. They told me that it was normal when both front and rear were set the same (72 deg, fan 3 for example) that the front air feels hot, but the rear feels cool.
When using Hi temp setting for the rear, after a minute or so, I could feel warm air-- at about the same temp as the front with 68 deg set.
A quick check of running the rear heater in Hi, with fan=3, and outside temp 55, showed an initial consumption of 2430 watts, gradually ramping down over 7 minutes to 1215 watts and stabilizing. At the lower level, on a long trip, I would lose 3.8 miles of rated range every hour.
My conclusion: try to use just seat warmers and front heater if possible. If that isn't enough, the rear heater consumption is not a show stopper unless I am cutting it close on range remaining at destination.

@Solarman004 , how do you measure AC power consumption in watts?

 

[Solarman004]

@Solarman004 , how do you measure AC power consumption in watts?

@hiroshiy If you are plugged into the wall charger, but not charging, then turn on climate control, above a certain power draw threshold, the HPWC will turn on and provide power for the climate control through wall power.
You can read the consumed current and voltage on the dash display. Multiply the two for power.

 

[Big Earl]

UPDATE: I finally had my service appointment and their conclusion was that nothing is wrong with my rear heater.
They recommended starting off rear heat on "Hi" then backing off the temp as the cabin heats. They told me that it was normal when both front and rear were set the same (72 deg, fan 3 for example) that the front air feels hot, but the rear feels cool.
When using Hi temp setting for the rear, after a minute or so, I could feel warm air-- at about the same temp as the front with 68 deg set.
A quick check of running the rear heater in Hi, with fan=3, and outside temp 55, showed an initial consumption of 2430 watts, gradually ramping down over 7 minutes to 1215 watts and stabilizing. At the lower level, on a long trip, I would lose 3.8 miles of rated range every hour.
My conclusion: try to use just seat warmers and front heater if possible. If that isn't enough, the rear heater consumption is not a show stopper unless I am cutting it close on range remaining at destination.

Another winter is fast-approaching and I think your service center appointment answered some questions for us. The issue is that the rear heating element seems to be about 1/3 as powerful as the front heater (~2 kW vs ~6 kW). As many have observed, turning the fan on high in the rear overwhelms the small heating element with too much airflow, resulting in luke warm air from the vents. For the best vent temperature and system performance, a moderate fan speed is probably the way to go to avoid the wind chill effect on rear passengers.

On my recent road trip in an X, I noticed that the rear air conditioning's performance was wasn't great. I think Tesla just undersized all of the components for the rear system hoping that it would be sufficient.

Sorry for the old thread bump, but I've been reading a lot about winter weather performance on TMC the past few days.

 

[Solarman004]

Another winter is fast-approaching and I think your service center appointment answered some questions for us. The issue is that the rear heating element seems to be about 1/3 as powerful as the front heater (~2 kW vs ~6 kW). As many have observed, turning the fan on high in the rear overwhelms the small heating element with too much airflow, resulting in luke warm air from the vents. For the best vent temperature and system performance, a moderate fan speed is probably the way to go to avoid the wind chill effect on rear passengers.

On my recent road trip in an X, I noticed that the rear air conditioning's performance was wasn't great. I think Tesla just undersized all of the components for the rear system hoping that it would be sufficient.

Sorry for the old thread bump, but I've been reading a lot about winter weather performance on TMC the past few days.

@Big Earl , here's another trick. On the front HVAC settings screen, select the airflow for both feet and dash vents. When you select the dash vents, the second row will get heated air from the center console vent (but not the side pillar vents). Since we rarely have passengers in the third row, this option, plus seat warmers, is more than sufficient to keep my kids warm in the second row, without turning on the inadequate rear heater.

 

[tommie]

Sounds a lot like my Audi Q5, which I traded in on my Model X100d. I paid for 3zone climate control, but the service man explained that meant driver, right side passenger, and rear seat got what the driver did. Hmm, seemed like 2 zones to me, but.....

 

[ditzpro]

I have a 6 seater and am experiencing the same problems..Ridiculous in a luxury car ..Heat and air should always be over engineered .
Blower speeds should never have to be set to highest ...This is just logical ...Small things like comfort make a big difference .What an embarrassment to be told by your rear passengers that "I'm cold , doesn't this thing have a heater "..Great car could be greater with a little attention ...

 

[Big Earl]

I have a 6 seater and am experiencing the same problems..Ridiculous in a luxury car ..Heat and air should always be over engineered .
Blower speeds should never have to be set to highest ...This is just logical ...Small things like comfort make a big difference .What an embarrassment to be told by your rear passengers that "I'm cold , doesn't this thing have a heater "..Great car could be greater with a little attention ...

Turning the rear fan up will not make it blow hotter air. Quite the contrary, as the increased airflow will overwhelm its small heating element. I'd recommend setting the rear temp to HI (I don't trust its sensor) and the fan speed to 3 or 4 for best results.

 

[Gwgan]

Dueling HVACs??
I was sitting in my seven seater MX in a parking lot under partly cloudy early afternoon low sun with an outdoor temp of 40F. The thermostat was set to 66F, Front HVAC on Auto, Rear HVAC manually on for dog on folded third row seats (overkill at these temps but it was colder earlier) but otherwise on Auto. Range Mode was off. My seat heater was on 1/3. The front fan was noticeably loud when it should have been barely on at all so I started playing with the screen controls. Fan was on 6 but cold air was coming out of the front vents. Rear fan was on 2 and warm air was coming out of the pillar vents. App said interior temp was 71F.
One unified temperature setting and front AC ramped up to cool the car while the rear HVAC continued to put out warm air?!?
I tried turning up the thermostat to above 71 and to Hi and warm air came out of the front vents. I also tried turning off the front AC but with the thermostat set back to 66F and the front fan slowed and warmish air started to flow. Rear output seemed unchanged. I wonder if I had let it go longer if the rear HVAC would have tried to cool the car alone.
I usually have the temp set to 66 if it is warm out or 68 if it is cold and do not usually monitor the actual interior temp but now I will start watching the auto choices more closely to avoid unnecessary energy use.

Is there an independent rear temperature sensor?
Why is there no manual control over the rear AC?
If the system thinks the cabin is too warm, why does it use AC instead of venting cooler outside air first?
Do androids dream?

Personally, I would rather the interior thermostat not be numeric since it cannot be accurate or even relatively meaningful without a posted interior temperature reading. I would prefer a colder-warmer gradient slider/dial with a max setting at the extremes for when I am in a hurry.

 

[hiroshiy]

Dueling HVACs??
I was sitting in my seven seater MX in a parking lot under partly cloudy early afternoon low sun with an outdoor temp of 40F. The thermostat was set to 66F, Front HVAC on Auto, Rear HVAC manually on for dog on folded third row seats (overkill at these temps but it was colder earlier) but otherwise on Auto. Range Mode was off. My seat heater was on 1/3. The front fan was noticeably loud when it should have been barely on at all so I started playing with the screen controls. Fan was on 6 but cold air was coming out of the front vents. Rear fan was on 2 and warm air was coming out of the pillar vents. App said interior temp was 71F.
One unified temperature setting and front AC ramped up to cool the car while the rear HVAC continued to put out warm air?!?
I tried turning up the thermostat to above 71 and to Hi and warm air came out of the front vents. I also tried turning off the front AC but with the thermostat set back to 66F and the front fan slowed and warmish air started to flow. Rear output seemed unchanged. I wonder if I had let it go longer if the rear HVAC would have tried to cool the car alone.
I usually have the temp set to 66 if it is warm out or 68 if it is cold and do not usually monitor the actual interior temp but now I will start watching the auto choices more closely to avoid unnecessary energy use.

Is there an independent rear temperature sensor?
Why is there no manual control over the rear AC?
If the system thinks the cabin is too warm, why does it use AC instead of venting cooler outside air first?
Do androids dream?

Personally, I would rather the interior thermostat not be numeric since it cannot be accurate or even relatively meaningful without a posted interior temperature reading. I would prefer a colder-warmer gradient slider/dial with a max setting at the extremes for when I am in a hurry.

Not sure about the temp sensor, but it sometimes show higher cabin temp in cold weather with some sunlight. Maybe the sensor is on close to the dashboard and affected by the sun?

Thus, usually at night, I think the cabin temp reading seems to be correct and I always have warm air from AC. However with sun up, in winter, I sometimes get cold air from AC.