Rear Vent AC Issues

Rear Vent AC Issues

Has anyone else experienced the following problem in their Model 3? I had climate control on auto (temp set at 69) and there was cold air blowing from the front vents, but warm/hot air blowing from the rear vents.

djharrington | 2018年4月2日

I've seen a couple other posts about this similar thing (rear vents not blowing) so I decided to test because I haven't actually thought about the rear vents before. At first I worried because I couldn't get any air to blow from the rear vents, hot or cold. Then I noticed a nifty button to actually blow air in back. In auto mode, nothing was blowing back there ... until I hit this button. Then it was a massive amount of hot or cold air depending on temp setting. The rear vents are much more powerful than Audis I've had.

Sjsato | 2018年4月2日

You are referring to the button on the screen for the rear seat vent, correct? I have mine activated but it only blows warm air, even when the AC is on and working in the front.

djharrington | 2018年4月2日

It wasn't an immediate transition from hot to cold for me

Turbo25 | 2018年4月2日

It appears that several recent threads are pointing to this issue...

Brian B | 2018年4月2日

Are you sure that the two are synced and not having their own temperature settings? I'm not sure if it has that capability, but that's what I could see could cause it. If it can't go separate for front and back, I couldn't see the two being different temperatures because they wouldn't be on separate cold/hot air supplies.

Turbo25 | 2018年4月3日

There aren't separate temperature settings for the front and rear vents, only a button within climate control that allows you to turn on the rear vents.

Jiong | 2018年6月10日

@Turbo25 I have the same issue. But I also found that when I set the temp well below the interior temp, the rear vent did blow cold air. But still not as cold as the front.
Have you found the reason and any fix?

s30319 | 2018年7月14日

Same issue here. I sat in back seat last night while showing friends and was shocked how hot the air is. Has anyone found resolution?

gtosnipey | 2018年8月3日

Same issue here it’s currently 76 outside and have the air on 71 and the rear vents are blowing out pretty warm air like it’s just fan circulation no AC. Just updated to 2018.26.3.

ADinM3 | 2018年8月4日

A slight tangent, but this thread has me wondering which temperature is used for the rear when the front driver and passenger controls are not sync'd. Is it the driver's setting of a blend of the two.

If so, are your front AC sync'd?

IntelSPE | 2018年8月4日

@turbo25 - I have exact same issue. Recently took car to SC. They confirmed issue but told that it is known issue and will be fixed in 2018.34 update. So we have to wait for 2018.34. SC didn’t give timeline when it will be released.

iliya.e.yordanov | 2018年9月25日

I am on 2018.36 and this issue just happened to me today (for the 2nd time actually). I had to manually set the AC to not be in Auto mode and then disable blowing air at the back, so that it doesn't drain my battery (hot air consumes a lot more battery than cold air). I hope they do fix it soon!

rbryan | 2018年9月25日

The car is smarter than you think, if no one is belted into the back the rear vents are closed unless you take it off automatic. Try it with someone belted in the back, on automatic the rear vent button lights up and air comes out.

gmkellogg | 2018年9月25日

If it's a belt sensor does that mean it will blow air with installed car seats using the seatbelt?

rbryan | 2018年9月25日

Good question about car seats, if there is enough weight it should, you can always trigger it on manual

wayne | 2018年9月25日

With our small dog nickeled into the middle seat the rear AC works consistently.

wayne | 2018年9月25日

Uh buckled.

ADinM3 | 2018年9月25日

Still curious and since no one answered previously, ...which temperature is used for the rear when the front driver and passenger controls are not sync'd. Is it the driver's setting of a blend of the two.

ADinM3 | 2018年9月25日

Still curious and since no one answered previously, ...which temperature is used for the rear when the front driver and passenger controls are not sync'd. Is it the driver's setting of a blend of the two.

rbryan | 2018年9月25日

My guess is the rear seat uses the drivers temp, the passenger temp is likely a plus or minus offset from the driver. But there is really no way to know.

mehingle14 | 2018年9月26日

I just picked my p.3d up today. I noticed the same issue. No matter what setting it was on, it was blowing 73 degrees out of the front, and felt like about 82 degrees out of the rear. Rlr that we picked up in early July did not have this issue. I'm going to call service about it in the morning.

rbryan | 2018年9月28日

I did a little testing sitting in the back seat with the driver and passenger temps set widely different (driver 68, passenger 80) and it seemed like the air coming from the passenger side rear outlet was warmer than what was coming from the drivers side.

PolTes18 | 2018年9月30日

Well same issue here on newest software. Tesla needs to fix it.

gwolnik | 2018年9月30日

I had the opposite problem, my passengers in the rear were complaining about the cold air blowing on them! We fixed the problem by blocking the rear vents with the folded up heat shield that I bought for the front window.

vmulla | 2018年9月30日

Same here. I had the issue earlier and a SC visit fixed it. But the situation is back again. Perhaps since the last update?

Both my kids in the back seat were buckled in and complained of the car being warm. I felt the rear went because I remember reading about these reports from others. Sure enough it was blowing warm air.

I just turned off the rear vent, and let the front vent do the work for the entire car. I tried a 2 thumb reset but there was no effect.

I'm waiting for ver9 to fix this bug.

mehingle14 | 2018年10月2日

So I made a service center request detailing my problem, even noting that I researched the forums and it looked like this was an issue that should have been fixed with software update 34.2.
I get a call from the service center yesterday, and the guy basically tells me that my theory was correct. The problem has not yet been fixed, as the engineers thought they had done with 34.2 (my car is not running 36.2).

service center tells me that the engineers are aware that they did not fix the problem with 34.2 and they are opining that the problem will not be fixed until update version 40.

the problem does not show up on my wife's long-range model, but was obvious from the start on my p.3d.

bottom line is that if your car has that problem, they are not going to be able to fix it until update 40, which will probably be months from now.

dwakelee | 2018年10月8日

Same issue for me - rear vents blow hot air while front track proper set temp. 926xx VIN (mid August build), 32.6 firmware. Hoping the post about an upcoming software version (40.x) being a fix prove to be true. Thankfully cold temps are coming to the northeast soon. In the meantime - it is quite annoying when the outside and front temps are a reasonable 70 degrees, and the temperature from the rear vents feels like the heating system is on. Thankfully I'm always in the drivers seat, but I do pay in the form of complaining from the rear passenger (10 year old son).

Drstein3000 | 2018年10月17日

Just got Model 3 last night. Zero air from back vent. Any solution yet ?

dwakelee | 2018年10月17日

Zero air from the back vent is a different problem. Make sure someone is in a rear seat, and that you have the rear vent enabled on the climate control screen. Perhaps try different modes as well (auto), as well as a reboot.

If you meant zero A/C or zero cold air, that is the problem currently lacking a solution. A handful of people also report the rear vents output too cold of air, but too hot is the most common.

PHLT3 | 2018年10月26日

I have the same problem:

M3 is running 2018.39.7.
Child seat buckled into back seat

Outside temperature: ~50F
inside temperature: comfortable
Set HVAC to auto / 70 degrees

The car turns on the AC as well as the rear vent. It blows cool air out the front vents (middle and feet) and hot air out the rear vents.

This seems like a huge waste of energy

1) why is it running the AC when it is 50 degrees outside? The windows don't need defrosting. Besides, it isn't blowing air at the windows

2) why is it blowing cold air to the front and warm air to the rear? That also seems like a waste as it has to heat air that it is cooling

3) why is it automatically turning on the rear vent. My guess is this is because of the car seat, although I haven't tried removing it to see.

To fix this, I turn off auto and turn off the AC as well as the rear vent. The car seems to then be comfortable.

I called Tesla customer support. They claim my car was showing no errors and that this is NOT a known software bug. They suggested I make a service appointment, which I did.

bb | 2018年10月26日

I reported this problem when I scheduled my service appointment. A Tesla service manager called me back to discuss it. He told me that the Model 3 has a single AC system that blows air through the same pipes and the rear vent can blow hot air when the batteries are running hot (as was my case, presumably, as I had been traveling at highway speeds for hours), as the air ducts that feed the rear vents run much closer to the batteries in the floor. As such, he told me that this is not something that can be "fixed" by a software update. His suggestion was to lower the AC temperature and direct the front vents to the back-seat passengers away from the front-seat passengers. I do not find that to be a good solution.

Note that when I did have my service call (for a rattling front door, which they fixed perfectly), I worked with the technician on this directly, but we could not reproduce the hot air blowing to the back seat. Presumably because the car (and batteries) were cold.

So, let us know if you only see this problem when the car is working hard, or if it happens all the time.

dwakelee | 2018年10月27日

@bb Interesting info. In my case my son noticed this during a 150 mi highway trip (part way into it, outside temp 70). So motor and battery likely warm. But not insanely warm outside temp, so I wonder how bad it is going to be when 80 or 90 outside?

The info you received also aligns with what many have said about lowering the front AC to finally get some cold out of the backs. Temperature rise from battery system 'sneaking' in could explain that for sure. I do wonder if this is really just poorly insulated, or if this temperature dump from the battery system is more intentional and required for battery temp management.

Temps in upstate NY have been cold since my first observation, so I'm not currently able to recheck under the same conditions. But in this now cold temperature case, if the service info you received is correct, I bet the vents will too blow of air vs. the fronts for the same reason (affected by battery system temp).

I can see how dumping some unwanted hot or cold from the battery system into the cabin is great for the battery system, but not great for the rear passengers. I hope there is some fix for this - I agree that work around is not a solution. Also, the hot blowing back vents can be turned off (which is what I did), but that effectively defeats the purpose. And you still need to freeze the front passengers to get enough cool for the back.

Would definitely like to hear if this new information correlates with what other people are seeing.

dwakelee | 2018年10月27日

Stupid no edit - was trying to say that I wonder if the rear vents may 'blow too cold' of air when battery is cold for the same reason. | 2018年11月7日

I'm having the same issue with warm air blowing out the back vents of my M3. My 11-month-old baby isn't crazy about it and neither am I.

I did find on a Reddit thread that someone got a response from Tesla saying that it was a known issue and would be resolved with firmware update 2018.36.

But I'm on 2018.42.3 now and it's still happening...

RedPillSucks | 2018年11月7日

I had the same issue as well. Couldn't reproduce it when I went to the SC

HAYSAMY | 2018年11月13日

I have the same issue as well.

dwakelee | 2018年11月13日

If it is the root cause that @bb reported a few posts up, probably every Model 3 has the issue. Will depend on driving duration, ambient temperature, and average speed - and if somebody is in the back seat to notice.

SalisburySam | 2018年11月14日

I noticed this happened once on an earlier version of firmware (now on 42.4), but I no longer see this behavior. Given that many folks here have the issue, may I suggest the following:

“Bug report: rear vent blowing much hotter air than setting and front vents” or words to that effect. Then you will know Tesla is actually getting this information, presumably from many owners, as an indicator that it is a widespread important owner issue.

PHLT3 | 2018年11月19日

I can confirm that 42.4 did not fix the problem as promised. I made another service appointment and the technician called me to discuss. I was told that this is a known issue that was supposed to be fixed in 2028.42.4 but was not. I was further told that multiple minor updates 2019.42.x will be coming through the new year which will have incremental fixes for this problem. A major update 2019.x will be out early in 2019 that should resolve the issue.

Or so I'm told by the tech who was reading the release notes...

tkammerer | 2018年11月22日

I put my French bulldog in the back seat in his car seat. The vents blow out brutally hot hair when my AC is set to 68 degrees. It only cools down when I turn temperature down to 65 degrees which is far too cold.

This is by far the worst thing about the model 3 currently. I really hope Tesla fixes this soon.

wayne | 2018年11月22日

I don’t have this problem with my Cocker Spaniel.

mattlptnschwrtz | 2018年11月23日

I have a cocker spaniel too but won’t let her ride in the car yet (she gets car sick and my seats are white). Regardless Same Issue yesterday with both kids in car seats, not fixed and my model 3 is brand new as of nov 20, and received update this week

vmulla | 2018年11月23日

I have the same problem. My kids in the back seat complain about this on longer trips.
I have a service appointment in a few days to have this looked at.
I'm turning off the rear vents to keep my kids comfortable.

rabadia12 | 2018年11月25日

Same problem here. Kids in back keep noticing the issue. With colder weather coming it shouldn’t be an issue. Hopefully this will be addressed before weather heats up again!

Ash | 2018年12月8日

I’m with the rest of you. I just found out about this issue this evening.

Has anyone spoken with support?

vmulla | 2018年12月8日

Update to my post on Nov 23.

I got my car back from the service center. Unfortunately they said they could not replicate the problem. - The problem only happens on longer drives, so I'm not surprised that they could not replicate the problem.

I discussed this further, and we agreed that I should return again in summer when the problem is truly a comfort issue. Right now its winter and warm air doesn't bother as much as it would in summer.

I shared the opinion from the forum that the air may be blowing over a hot battery and thus causing some warming. The tech disagreed and said there isn't any ducting that gets as close to the battery to make a difference. However he did share that its the same AC that blows air to both front and back vents.. That doesn't make sense to me. A software version was updated so the cause isn't software either.

As it stands the issue is unresolved, the rear vent still blows hotter air than the front - its actually significantly warmer in the back on longer drives.

jake | 2018年12月10日

So I did a ~1,000 mile road trip this Thanksgiving from WA to MT. It was pretty cold the whole way (~20s, 30s F). I had the temperature inside set to 68 F the whole time and it was a constant struggle to get the back not to overheat.

We had 4 people in the car the entire time and I was fine in the drivers seat but the air in the back was HOT. So much so that I had to manually drop the temperature and blast out the hot air occasionally.

My theory is is that the air flows along the ground to the back, right above the battery. I assume my battery was nice and toasty from driving and supercharging all day. If this is the case, I am not sure how they would fix it.

I also noticed the floor gets quite warm, I assume because of the toasty battery.

I will also note that I had ~70% battery efficiency the whole way, which seems a little low. I wonder if it really was heated air. I hope Tesla adds some dumbed-down energy stats that tell you where your energy usage comes from (driving, heating, AC, USB peripherals, etc.).

vmulla | 2018年12月10日

I heard the theory of air blowing over the battery and shared it with the tech, he said that's not possible since the ducting is well seperately from the battery.

Anyway, the way I deal with it is by turning off the rear vents and making the front vent blow to the backside along the roof. That work around suits my comfort preferences.

I'm hoping the solution is made in time for summer. It has to be a software fix, because I had the problem, it was fixed and then it returned.

vmulla | 2018年12月10日

well seperated*

finman100 | 2018年12月10日

I'm pretty sure Tesla doesn't let the battery "get nice and toasty" and thus give off too much heat.

Tesla TMS is by far the best in the biz.

If the TMS is doing its job at all, it would moderate the battery temp between some tight temp fluctuations for a longer lasting pack. You know, 'cause we all keep our cars for 10 years or more and want the same range as when new...