HVAC question
Hi guys and gals. Does anyone know if the heater and ac in M3 draw a linear amount of power no matter what temp you’re requesting? I’m used to cranking the heater when it gets cooler out 
but if running it less than on HI will save I guess I’ll need to adjust.
but if running it less than on HI will save I guess I’ll need to adjust. 0
Comments
What is cool (pun intended) is the compressor runs at a variable rate depending on need. ICE cars use a clutch connected to the engine. So the compressor is on or off, and the speed is controlled by the motor speed, which is often unrelated to cooling needs. Seems like a Rube Goldberg system in comparison with Tesla's system.
That’s more the info I was wondering. Maybe I should have phrased the question differently (3am pop up idea Lol). From the little I understand about vehicular HVAC iCE motors seem to produce the same amount of heat no matter what and a dial controls the amount of heat that enters the cabin. Obvi that’s not great in an EV. Thanks for the input guys. Out of curiosity is there a better heating system than the “resistive”? Does Model X/S employ something better?
Are there more efficient heating methods? Yes. Heated seats are far more efficient because you’re heating a much smaller area, so need a lot less heat. A heat pump would be much more efficient - but would only work down to around freezing or so; you’d have to equip the car with resistive heaters anyway to deal with sub freezing conditions, which would raise costs. The Leaf, if I’m not mistaken, used a combination of heat pump and resistive heating.
a) As good will, no charge at all
b) Labor is good willed, just the $35-ish price for new filters
c) $125, as reported above. (If this includes the filters, suggests about $85 in labor.)
d) just under $200, as reported by several (includes filters)
e) $233 and no good will to do the decontamination (includes 2 filters that didn't need replacement - I got them back)
I'm sure there are additional variants, but I am getting really peeved at Tesla's willy-nilly approach to the problem and what they are charging to (temporarily) fix it.
It takes one torx t15 (iirc) screwdriver. The only difficulty is that the screw is difficult to access.
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+1
I'm trying to set the HVAC to ventilation only, I mean, I want the system to just turn the fans and blow air from the outside, avoiding heating, cooling and ACing ... is that possible at all?
What I see is that it is not possible to avoid the temperature set point, therefore the system will blow either heated or cooled air, never the plain natural air.
Is there a trick to overcome the problem?
Cheers,
Ezio
Yes I did, but nevertheless:
>There is no way to prevent the heater from coming on
Exactly. That's what I want to avoid.
In good old cars, there is a nice knob that does the heather/cooler switch off, you just tune the air intake by adjusting the fans, pretty useful when outside air is at the right temperature, that is, most of the time.
With the M3, the option is to turn off completely the climate control and open the windows: noisy, uncomfortable, and power consuming.
Besides, the automatic temperature control is not really "smooth" like in ordinary cars. When I turn on the AUTO mode, you either get frozen or steamed, alternatively. Quite unpleasant environment. It's not just me, I had a lot of complaints from passengers also.
Is it that the temperature sensors in my M3 are defective or is it a glitch in the climate control design?
Now for your "besides..." just like in other cars, and for HVAC in general, humidity matters, as does airflow on you and the passengers. 72 while on A/C is not the same as 72 on heat. I have to adjust the temperature the same as I did in my last "ordinary" car. The only exception is the stupid heater coming on when I don't want it to come on.
But to prevent the problem from happening in the first place I learned to change to internal air-flow when the A/C is on. That way you're not dehumidifying/cooling a ton of air, just what's in the cabin and the humidity that seeps in. This greatly reduces condensation created by the A/C. It's also much more efficient.
Some cars do this by default when you turn on the A/C, but some don't and M3 is one of those
The "besides" point is more tricky. I understand your point re. humidity and subjective perception with A/C on vs. A/C off.
This is not the problem, trouble is experiencing wild temperature fluctuations while on AUTO mode.
Unlike other cars, M3 alternatively blows chill wind so everybody freezes (when temperature is above the set temperature) AND furnace hot air so everybody sweats (when temperature is below the set temperature).
Other cars don't have these extreme hot/cold fluctuations when in AUTO mode, they gently regulate airflow and air temperature so the car inside stays around the desired temperature.
Therefore the question is: is it because of a defective sensor (that can be fixed) or is it a defective design of the HVAC system?
Now I will concur, in regards to winter time and heater usage, that because of the way the heater works and the way the human body feels airflow...that after the cabin gets up to set temp, the heater turn down too low, if on at all, which causes the air blowing in the cabin to feel cool. Air at the set point temperature(when heating is required in winter), will feel cool to the human body.
In ordinary cars and in a very simplistic explanation, that have heat pumps, you have a hot water supply which is where the air blows across to give you your cabin heat...this maintains its temperature and the only thing that varies is the fan speed. This gives you "warm" air for your body to feel.
In the winter time, I tend to set the set point higher, but then adjust the airflow so that it doesn't blow directly on me.
The HVAC is designed as it is designed and is functioning as such. There are many ways to do things, and one way isn't necessarily "better" than another depending on the application.
I can't explain myself clearly, so let me make an example.
In my former car, a BMW X1, if I set the AUTO temperature to 24° C (75 °F) the inside of the car is kept somewhere between 23 and 25° (73-77), regardless of outside temperature, humidity or winter/summer subjective perception.
The airflow provided by the car also is somewhere near the 25° set point ... you feel comfortable.
Fast forward to M3, if I set AUTO temperature to 24°, at some point i get an air inflow of say 15° (59 F) and everybody's chilling, this cools the car, so that temperature will eventually go below 24°, at that point the fans start flooding with say 32° (90 F) and everybody's sweating ... after a while the car temperature will go over 24° and the chilling cycle will restart, and so on ... freeze-bake-freeze-bake.
This is what I mean by wild fluctuations.
People get annoyed and start complaining about how uncomfortable the M3 is ... reminds me of the old italian trains of the '80s :-)