Is very weak rear heat normal on Model X?

[drewg123]

I have a new-config 7 seater and just got back from a week long road trip where the first and last days were done in "cold" (roughly 30F) weather. The front was reasonably comfortable, but my son complained about being cold in the 2nd row. I did some controlled tests after I got home.

In our garage, with the car plugged in, and ambient temps of ~55F, car interior at 60F according to the app, and with the front and rear both set to "hi", the front vents emit very warm air. The rear vents all emit luke warm air. I should probably get a better thermometer so I can quantify it. Shouldn't the rear vents also be blowing hot air?!?

One interesting thing I learned when playing around like this is that the 2nd row center vents (attached to the front row's center console) seems to be controlled by the front, not rear, climate control. It is treated as one of the upper front vents when controlling things manually. Is this expected?

Another "interesting" thing we learned on the trip is that the air temp emitted by the front vents seemed to vary with speed. Eg, the air was not very warm at 75Mph, but was nice and warm while we were sitting at the supercharger. As I'm writing this, I'm wondering if this could be due to range mode?

 

[JohnSnowNW]

I have not noticed the rear vents being particularly weak, but I don't spend a lot of time back there. I have been asked to turn the heat down before, but that's not particularly quantifiable.

Yes, the vents in the center console are tied to the "Front," which I also found a bit odd/unexpected.

Range Mode will definitely affect climate control.

 

[drewg123]

I have not noticed the rear vents being particularly weak, but I don't spend a lot of time back there. I have been asked to turn the heat down before, but that's not particularly quantifiable.

Yes, the vents in the center console are tied to the "Front," which I also found a bit odd/unexpected.

Range Mode will definitely affect climate control.

Range Mode should not impact anything when sitting plugged in & charging in my garage though, right?

I don't spend time back there either... hence the controlled tests. Unless somebody chimes in saying its normal, I'll ask the SC about it. I'm due to go in soon for them to install a forgotten tow package.

 

[Solarman004]

Long running issue. See this thread: MX Rear Heat Performance

 

[JohnSnowNW]

Range Mode should not impact anything when sitting plugged in & charging in my garage though, right?

That I can't answer. Range Mode also disables the DRL's, and I don't believe they come on when you're plugged in. That is to say, I wouldn't assume that the parameters of Range Mode are affected by certain conditions.

It sounds like from the above linked thread that the 3rd row vents just don't warm up that fast, or they're considerably less efficient than the front vents...and thus operating normally in your case.

Surprised I hadn't come across that thread until now.

 

[SMSMD]

I have a new-config 7 seater and just got back. As I'm writing this, I'm wondering if this could be due to range mode?

Yes,the heat to the rear is weak and the blower irritatingly loud, my three kids carry their soft snuggies with them to keep warm. I never sat in the back my kids say it sucks.
Our butt warmers are always on.
The drivers and passengers legs get uncomfortably cold. I and my wife wear thermals and it was extremely comfy in the - 16°C.
The best thing we did was to use the sunshade. It helped in keeping our heads warm and also increased our range slightly.
Never used range mode though so can't comment on that .
Looks like you did not have defrost issues !
Just travelled Banff and lake Louise in Alberta Canada .

 

[GOPJEW]

Range mode 100% limits heating - period, end of discussion.

However, as others have noted there is a long running thread about the power/efficiency of the rear system, and if you are using Range Mode you are further limiting its abilities to heat.

I think you have a compound problem, it’s limited effect - particularly in the 3rd row - in normal mode and then you were using Range Mode.

Use the seat heaters - they are actually VERY effective - more so than my S that’s for sure.

 

[Solarman004]

The best thing we did was to use the sunshade. It helped in keeping our heads warm and also increased our range slightly.

To go one step further, I bought a small roll of foil-faced bubble wrap insulation from Home Depot. I cut a piece 1/4" smaller than the sunshade around the full perimeter. When I install the sunshade with the bubble wrap sandwiched between the glass and the shade, the shade holds it in place. The amount of cold air dropping on the driver's and front passenger's heads decreases dramatically.

It sounds like from the above linked thread that the 3rd row vents just don't warm up that fast, or they're considerably less efficient than the front vents...and thus operating normally in your case.

The rear heater and fan are located in far aft, right corner of the MX. This is why the airflow is much stronger in the 3rd row than the 2nd. You can also feel a significant temperature drop as you get to the 2nd row vents. This is why I suspect (but can't prove) that a primary cause is uninsulated ducts running along the cold outer skin and losing heat to the outside.

 

[drewg123]

Thanks for the pointer to the other thread. From the measurements in the other thread, it sounds like the rear heater is just undersized vs the front (6kw vs 2kw).

And thanks for the pointer to the location of the heater. I'll try the "set rear to hi, front to a reasonable temp" trick from that thread for our drive on Christmas day.

It sounds like the warmest spot in the rear may be in the 3rd row, passenger side. I also wonder if maybe closing the 3rd row vents would help 2nd row comfort.

Does anybody know where the thermometer for the rear climate control is located?

 

[Solarman004]

Thanks for the pointer to the other thread. From the measurements in the other thread, it sounds like the rear heater is just undersized vs the front (6kw vs 2kw).

And thanks for the pointer to the location of the heater. I'll try the "set rear to hi, front to a reasonable temp" trick from that thread for our drive on Christmas day.

It sounds like the warmest spot in the rear may be in the 3rd row, passenger side. I also wonder if maybe closing the 3rd row vents would help 2nd row comfort.

Does anybody know where the thermometer for the rear climate control is located?

Sorry, I don't know where the rear temp sensor is located.
I can't remember if I posted this in the other thread but here is another trick we use in our 6-seater with the third row empty (family of 4): Keep the rear heater off. Set the front heater source to include the dash vents. With this selection, the 2nd row gets heat through the center console vent (but not the pillar vents). This plus seat warmers keeps my children quite comfortable and without the large power consumption of the rear heater.

 

[SMSMD]

To go one step further, I bought a small roll of foil-faced bubble wrap insulation from Home Depot. I cut a piece 1/4" smaller than the sunshade around the full perimeter. When I install the sunshade with the bubble wrap sandwiched between the glass and the shade, the shade holds it in place. The amount of cold air dropping on the driver's and front passenger's heads decreases dramatically.

This is what I use on long winter trips with my family..both for the windscreen and the falcon wing door.

 

[Solarman004]

This is what I use on long winter trips with my family..both for the windscreen and the falcon wing door.

@SMSMD , that is the same material I use above my sunshade.
How do you get it to stay against the FWD windows? Do you use foam rubber for a friction fit? I still have half a roll left and would like to make covers for the FWDs.
Thanks.

 

[SMSMD]

@SMSMD , that is the same material I use above my sunshade.
How do you get it to stay against the FWD windows? Do you use foam rubber for a friction fit? I still have half a roll left and would like to make covers for the FWDs.
Thanks.

I took a news paper and drew a outline of the falcon wing door upper glass pressing against the glass , used the outline to cut out the bubble wrap, just a fraction oversize than the newspaper outline.
You can push the bubble wrap in space between the glass and the headliner very snug fitting, does not need any adhesive.
Hope this info helps you.

 

[Solarman004]

I took a news paper and drew a outline of the falcon wing door upper glass pressing against the glass , used the outline to cut out the bubble wrap, just a fraction oversize than the newspaper outline.
You can push the bubble wrap in space between the glass and the headliner very snug fitting, does not need any adhesive.
Hope this info helps you.

Thank you! I will give that a try.

 

[jerry33]

Range Mode should not impact anything when sitting plugged in & charging in my garage though, right?

That's not correct. You always want range mode off when plugged in, otherwise battery heating and cabin heating will be affected.

 

[drewg123]

Thanks all. Between turning off range mode, and manually adjusting the rear heat to high with a low fan speed, we were comfortable in the 30F (which is cold for us ) round-trip yesterday.

 

[jbwinton]

Yes,the heat to the rear is weak and the blower irritatingly loud, my three kids carry their soft snuggies with them to keep warm. I never sat in the back my kids say it sucks.
Our butt warmers are always on.
The drivers and passengers legs get uncomfortably cold. I and my wife wear thermals and it was extremely comfy in the - 16°C.
The best thing we did was to use the sunshade. It helped in keeping our heads warm and also increased our range slightly.
Never used range mode though so can't comment on that .
Looks like you did not have defrost issues !
Just travelled Banff and lake Louise in Alberta Canada .

rear heater in MX is unacceptably bad. Mine has been in the shop a few times and they tell me "try this setting; turn of that." doesn't matter. it's still no good and apparently no way to fix.

specifically, at 35F today I preheated the car for 45 minutes. then used rear heat on MANUAL/HIGH. I kept checking and got cold air out of rear pillar vent UNTIL after driving for 55 min. Tech said to turn OFF "range mode" so I did that and tried on the way home. same deal. except worse. the car was in my heated (70F) factory and plugged in. when I drove home the rear vents were still blowing cold air when I got home. No way the battery could be very cold when it was in a 70F space for 8 hrs!!

 

[jbwinton]

Yes,the heat to the rear is weak and the blower irritatingly loud, my three kids carry their soft snuggies with them to keep warm. I never sat in the back my kids say it sucks.
Our butt warmers are always on.
The drivers and passengers legs get uncomfortably cold. I and my wife wear thermals and it was extremely comfy in the - 16°C.
The best thing we did was to use the sunshade. It helped in keeping our heads warm and also increased our range slightly.
Never used range mode though so can't comment on that .
Looks like you did not have defrost issues !
Just travelled Banff and lake Louise in Alberta Canada .

 

[jbwinton]

rear heater in MX is unacceptably bad. Mine has been in the shop a few times and they tell me "try this setting; turn of that." doesn't matter. it's still no good and apparently no way to fix.

specifically, at 35F today I preheated the car for 45 minutes. then used rear heat on MANUAL/HIGH. I kept checking and got cold air out of rear pillar vent UNTIL after driving for 55 min. Tech said to turn OFF "range mode" so I did that and tried on the way home. same deal. except worse. the car was in my heated (70F) factory and plugged in. when I drove home the rear vents were still blowing cold air when I got home. No way the battery could be very cold when it was in a 70F space for 8 hrs!!

and it's embarrassing to tell friends in the middle seat (7 seater) that in my $100k car the rear doesn't work when they say "we're cold back here"

 

[ditzpro]

I agree with jbwinton ...This car with all the tech should be able to run you out with heat ..Most of our trips do not have a range problem .
They are comfortably short enough (daily to work or store , gym Etc) to be within the battery .
For the long trips , judgement can be used ..Otherwise , give me all the heat I want .
It is embarrassing to have people in the back yell for more heat .