G12 Ambient Air Temp Not Reading Correctly

[forrby]

The ambient air temperature for my G12 is not reading correctly and seems to be reading a higher temperature than it really is. Yesterday it was around 81°F, but it read 90°F. This is admittedly a champagne problem but the issue I’m having is when my car preconditions in the morning it thinks it’s 78°F when it’s really 67°F. I run hot so I like colder temperatures but when you’re just wearing shorts and a t-shirt, it’s already 67°F and you hop into a car that’s even colder than that, it’s quite a shock. Not sure when this issue started but I did read that for some BMW’s the ambient air temperature is around the lower part of the front bumper. I’m not sure if that’s the case with the G11/12 but I did install a front splitter a couple of months ago and I’m worried that I may have damaged the ambient sensor in doing so. Or is this a common issue with G11/12s? Any information would be absolutely appreciated!!

[M_Bimmer]

Exterior temperature sensor used by your DME, and is available on your instrument cluster, it location and orientation, as depicted in post #2, could indeed be impacted by a splitter installation. https://www.7post.com/forums/showthread.php?t=1718871

The interior HVAC system uses a separate cabin temperature sensor that is located on the temperature control panel. Not sure how you are determining that the displayed temperature set value is off (driver's side and/or passenger side).

I didn't catch your vehicle information (pre-LCI or LCI, MSPORT, or ?), so if provide a little more info, I'll adjust my response accordingly.

Cheers.

[Raimo5]

Ambient temperature sensor can deviate from actual temperature in many scenarios. It can read hotter or colder after a period of idle sitting, or read hotter some time after driving due to heat saturation coming from hot engine bay. This should generally be withing +/-3 degrees Celsius. During driving, these sensors are very accurate as there is constant airflow over the housing. That said, there shouldn't be such a large deviation in morning when car has sat overnight and modifications dont play a role. These temperature probes are cheap so I would replace it to eliminate possible fault with that.

Unless you drive a hybrid with eclectic A/C compressor, then there is no cooling as part of preconditioning. Above 15c/60f, preconditioning ventilates outside, non-conditioned ambient air into vehicle cabin. Below those temps, you will get heating if you have Auxiliary Heating package.

[forrby]

Ohh that’s very interesting! I do have a Hybrid so that may be why the temperature is so much different in the morning. So your saying for non-hybrid cars if the temp is above 15c/60f the preconditioning does not turn on A/C, it only ventilates outside air into the cabin. For my hybrid 745e when it’s preconditioning, the AC is actually on when I get into my car, even if the outside temperature is only 67°F. I was thinking that the preconditioning would be set to the temperature that my thermostat was last set on but maybe it just puts it on full blast when it’s above 15c/60f. Again in a month or so when it’s hotter this would be fine, but for right now in the morning it’s only around 67°F. When I get in the car the AC is going full blast and it feels like 60° or less, plus seat ventilation set on max, and I’m only wearing shorts and a T-shirt so it’s quite a shock. I’m going to put a smart thermometer in the cabin to see exactly what’s going on there when it’s preconditioning. Thanks for the info!

[Raimo5]

Originally Posted by forrby

Ohh that’s very interesting! I do have a Hybrid so that may be why the temperature is so much different in the morning. So your saying for non-hybrid cars if the temp is above 15c/60f the preconditioning does not turn on A/C, it only ventilates outside air into the cabin. For my hybrid 745e when it’s preconditioning, the AC is actually on when I get into my car, even if the outside temperature is only 67°F. I was thinking that the preconditioning would be set to the temperature that my thermostat was last set on but maybe it just puts it on full blast when it’s above 15c/60f. Again in a month or so when it’s hotter this would be fine, but for right now in the morning it’s only around 67°F. When I get in the car the AC is going full blast and it feels like 60° or less, plus seat ventilation set on max, and I’m only wearing shorts and a T-shirt so it’s quite a shock. I’m going to put a smart thermometer in the cabin to see exactly what’s going on there when it’s preconditioning. Thanks for the info!

Thanks for clarifying that. Also, is it a new occurrence or has it been like this all along? Do you have heating/cooling issues during driving as well or only during preconditioning?

And yes, with internal combustion cars there is no additional conditioning of incoming air. It's just not possible as A/C compressor is driven by a belt off the engine crank pulley, and engine is not turned on for that purpose. Exception would be cars with option SA1CR. For hybrids, they install electric compressors, as you can cover long distances with ICE never having to turn on. With A/C compressor producing cold air during preconditioning, then I would assume it would follow the set temperature in HVAC control panel and not overcook it. At least with heating option (below 15c/60f) it does that. Perhaps set higher temperatures on HVAC panel and disable A/C button for a test one night to see how it behaves next morning when you precondition. Oh and does it also ventilate seats during preconditioning? I didn't know it does that.

[forrby]

Originally Posted by Raimo5

Thanks for clarifying that. Also, is it a new occurrence or has it been like this all along? Do you have heating/cooling issues during driving as well or only during preconditioning?

And yes, with internal combustion cars there is no additional conditioning of incoming air. It's just not possible as A/C compressor is driven by a belt off the engine crank pulley, and engine is not turned on for that purpose. Exception would be cars with option SA1CR. For hybrids, they install electric compressors, as you can cover long distances with ICE never having to turn on. With A/C compressor producing cold air during preconditioning, then I would assume it would follow the set temperature in HVAC control panel and not overcook it. At least with heating option (below 15c/60f) it does that. Perhaps set higher temperatures on HVAC panel and disable A/C button for a test one night to see how it behaves next morning when you precondition. Oh and does it also ventilate seats during preconditioning? I didn't know it does that.

I’ve only had the car since September 2023 and I did not start utilizing the preconditioning until the winter time. During the winter time the preconditioning was fine and the interior would be noticeably warmer when it was below 60°F outside. It was only in the last month when it started to warm up here in Texas and I noticed that when I got into my car, preconditioning would make the cabin freezing when it was only about 66°F to 68°F/ ~19°C outside.

For the most part, heating and cooling seems to be OK while driving, but I did notice one thing that’s kind of the opposite of what’s happening during preconditioning.

I try to be as energy and fuel efficient as possible so I typically stay on Hybrid Eco Pro mode. This will decrease the amount of power going to the AC along with some other things. With fuel efficiency in mind, when it’s warmer like 80°F+, I try to keep the thermostat around 72°F to 73°F/ 23°C. I run pretty hot though so to be truly comfortable I usually like it around 69°F. Anyways, when it’s warmer and I start a drive, the AC will go on full blast to drop the temperature down in the cabin. Then I believe from the previous BMWs I’ve had, usually the AC will kind of take a step down just to maintain the temperature.

However, I’ve been noticing that for this car, after the cabin cools down initially, it will then start feeling a little warmer than the first few minutes of the drive. And I definitely feel it because like I said, I usually like to have it around 69°F, so 73°F is already the maximum discomfort I’m willing to sacrifice. So when it starts to get warmer than that I’ll have to either drop the thermostat temperature or increase the fan speed. I’m not sure if this is because of being on Eco Pro or what, but I would expect a flagship car to do a very good job at maintaining the temperature set on the thermostat. It may also just be because the sun is starting to come out and heating up the roof, I’m not quite sure. This will be my first Hot season with this car so I guess I’ll have to experiment with it a little bit.

I did notice one thing yesterday when it was around 81°F and I was sitting in my car installing a few things. I had the AC on for maybe about 20 to 30 minutes while the car was parked. When I finished and left the car, I noticed that there was a puddle of water coming from around the bottom of the front left side wheel. I don’t know if this is just typical condensation from any AC running while stationary, but I just never noticed this kind of a puddle before. I wonder if it has anything to do with the possible defective vapor insulation valve you mentioned in a different post.

I’m not sure if the preconditioning ventilates the seats, I’ll try to check that out tomorrow morning. However, I do have a climate control rule set so that when it’s above 55°F, the ventilated seats automatically turn on to fan speed 3. I believe this happens after you turn the car on.

[F90bmwmastertech]

Originally Posted by forrby

The ambient air temperature for my G12 is not reading correctly and seems to be reading a higher temperature than it really is. Yesterday it was around 81°F, but it read 90°F. This is admittedly a champagne problem but the issue I’m having is when my car preconditions in the morning it thinks it’s 78°F when it’s really 67°F. I run hot so I like colder temperatures but when you’re just wearing shorts and a t-shirt, it’s already 67°F and you hop into a car that’s even colder than that, it’s quite a shock. Not sure when this issue started but I did read that for some BMW’s the ambient air temperature is around the lower part of the front bumper. I’m not sure if that’s the case with the G11/12 but I did install a front splitter a couple of months ago and I’m worried that I may have damaged the ambient sensor in doing so. Or is this a common issue with G11/12s? Any information would be absolutely appreciated!!

I can tell you that, as a BMW dealer mastertech, its possible you need a new instrument cluster. I had a g12 a few months ago that would read about 5-15 deg off and we started with a new ambient air temp sensor, no change, checked the wiring, no fault, ended up being the instrument cluster. If your car is under warranty bring it in and make them fix it. The ambient air temp sensor is on the passenger side behind the wheel well trim so its alot less likely to mess it up than on some of the older eseries cars.

[Raimo5]

Originally Posted by forrby

However, I’ve been noticing that for this car, after the cabin cools down initially, it will then start feeling a little warmer than the first few minutes of the drive. And I definitely feel it because like I said, I usually like to have it around 69°F, so 73°F is already the maximum discomfort I’m willing to sacrifice. So when it starts to get warmer than that I’ll have to either drop the thermostat temperature or increase the fan speed. I’m not sure if this is because of being on Eco Pro or what, but I would expect a flagship car to do a very good job at maintaining the temperature set on the thermostat. It may also just be because the sun is starting to come out and heating up the roof, I’m not quite sure. This will be my first Hot season with this car so I guess I’ll have to experiment with it a little bit.

This behavior seems normal, especially in Eco Pro modes. Those new A/C compressors, be it either electric or belt driven, really embrace EfficientDynamics to its fullest. In doing so, it maintains lowest needed operating loads that are required to keep evaporator at required temperature. I recall there are also coding differences (that can be changed) between different market regions when it comes to A/C power. Try it in other driving modes as well to see if these alleviate complains - just so we know if it is caused by Eco Pro mode.

Also worth noting is that initial cooling is always more powerful to bring cabin temperatures down faster. It might not even be that cabin is getting warmer after that initial cooling, but you start feeling warmer because there is less windchill from lower fan speeds. In automatic fan mode, solar sensor is also tracking sun angles to redirect airflow as needed to keep occupants comfortable while maintaining lowest load on A/C.

Personally I find that A/C is potent enough that I have only driver zone venting activated during summer when I drive alone, fan control Auto with speed 2.

Originally Posted by forrby

I did notice one thing yesterday when it was around 81°F and I was sitting in my car installing a few things. I had the AC on for maybe about 20 to 30 minutes while the car was parked. When I finished and left the car, I noticed that there was a puddle of water coming from around the bottom of the front left side wheel. I don’t know if this is just typical condensation from any AC running while stationary, but I just never noticed this kind of a puddle before. I wonder if it has anything to do with the possible defective vapor insulation valve you mentioned in a different post.

This is completely normal. The hotter and more humid the air is, the more condensation will accumulate. Considering that these evaporators can run near freezing temperatures, then lots of condensations is nothing to worry about. Just like a cold glass of beer during hot summer day.

Originally Posted by forrby

I’m not sure if the preconditioning ventilates the seats, I’ll try to check that out tomorrow morning. However, I do have a climate control rule set so that when it’s above 55°F, the ventilated seats automatically turn on to fan speed 3. I believe this happens after you turn the car on.

Yeah, the conditioning rule is probably what turns them on at vehicle entry. These should not be running as part of preconditioning.

Originally Posted by F90bmwmastertech

I can tell you that, as a BMW dealer mastertech, its possible you need a new instrument cluster. I had a g12 a few months ago that would read about 5-15 deg off and we started with a new ambient air temp sensor, no change, checked the wiring, no fault, ended up being the instrument cluster. If your car is under warranty bring it in and make them fix it. The ambient air temp sensor is on the passenger side behind the wheel well trim so its alot less likely to mess it up than on some of the older eseries cars.

That is really interesting. Was it BMW technical support that advised KOMBI replacement? If yes, then I wonder if there is a known chip issue with clusters. I also have to wonder how it would have reacted to software update/reflash.

[forrby]

Originally Posted by F90bmwmastertech

I can tell you that, as a BMW dealer mastertech, its possible you need a new instrument cluster. I had a g12 a few months ago that would read about 5-15 deg off and we started with a new ambient air temp sensor, no change, checked the wiring, no fault, ended up being the instrument cluster. If your car is under warranty bring it in and make them fix it. The ambient air temp sensor is on the passenger side behind the wheel well trim so its alot less likely to mess it up than on some of the older eseries cars.

Thank you so much for this information! I think you may be right. Do you think the defective instrument cluster could have anything to do with my interior cabin temp being a little off? Also, is there any danger in having the instrument cluster read a higher temperature than it actually is?

Here are some temperature readings from this morning.

First drive of the day 8:30AM
-iPhone weather: 72°F
-Instrument cluster: 76°F
-Preconditioning: 70°F (last night I left thermostat on Auto 70°F and today when I entered the car, thermostat preconditioning was set at Auto 70°F )
-Bluetooth Cabin temp: 59.2 °F
-For some reason my steering wheel was activated after driving even though my climate control rule is only set to activate steering wheel heater below 23°F

2nd drive of the day 9:50AM
-iPhone weather: 72°F
-instrument cluster after 5 minutes of driving (partially on highway): 78°F

Third drive of the day
-iPhone weather: 82°F
-instrument cluster after 15 minutes of driving: 87°F

Fourth drive of the day 6:50 PM
- iPhone weather weather 77°F
- Instrument cluster after 8 minutes of driving 84°F

[Raimo5]

Originally Posted by forrby

Do you think the defective instrument cluster could have anything to do with my interior cabin temp being a little off? Also, is there any danger in having the instrument cluster read a higher temperature than it actually is?

Yes, it can affect it. Outside air temperature has influence on HVAC calculations that are used for cabin conditioning. KOMBI is also a master module that sends out damped ambient temperature information to CAN and MOST bus, where other modules that require ambient temperature information will get it from. It can have significant influence on internal operating maps of DME/DDE and VDP.

That said, your deviations are not too large, but consistently higher and possibly causing undesirable HVAC behavior. I would take it to dealer or indy for proper diagnosis. ISTA has different service modules for this sensor and faulty temperature reading on cluster. Especially if you are under warranty.