Auto Temp setting?

[ricshaw]

I'm not sure if my auto temp is working properly. I have an 08 328i and whenever i hit the AUTO temp button - the temp will turn on to the temp i left it off on - say if it's 25 degrees outside and i put it on let's say for example 70 the day before. When i turn on the AUTO shouldnt it be set to 84 degrees? Mine doesnt. Also, whenever i turn on auto, the fan goes all the way to full blast and the AC turns on. Is this normal or should i go into the dealership?

i remember when i first bought my car - it was warm outside and then it turned night and when i went into my car the temperature adjusted to the outside temp.

[dallasfan824]

Im having a hard time figuring out what you are asking.

[blitz102]

I don't think it will automatically reset to whatever you left it on. it adjusts to the temperature of the car while you are in it. so for example if you set it to 74, it maintains the 74 degree temp while you're in it.

also, when you press auto the manual says it turns up the cool a/c to get the car cool fast.

hope that helps.

i just leased an 09 328 sedan and am still getting used to it. the one thing i was wondering is whether there is a way to synchronize the passenger temp with the driver's side (so you don't have to adjust both knobs...that way if it's just me in the car they're both set to the same temp). any thoughts from anyone?

[Beer Goggles]

There is no SYNC for temps. Strange but none. And AUTO just means it adjust the fan and temp to get the car to the temp you have set. It has nothing to do with the outside temp.

I know in my Audi it did adjust the fan sped if it was close to the temp outside, but that annoyed me.

[sor]

The way it should work is that it adjusts the output to the inside temperature. This may seem like it's reacting to the outside temp, but only because the temp inside and out is usually about the same if the car is left off awhile.

So, for example, if the car's temp is 40f inside the cabin and you've got it set to 70f, it's going to blow hot air hard. As it warms the cabin and that 40f becomes 60f, it's going to blow hot air softly. Cooling works pretty much the same. One nice thing is that when it's cold outside it seems to wait until the car has warmed up a bit so it doesn't blow cold air hard before it can heat the air properly.

Also not sure on the reset or whatever it is you're experiencing regarding whatever temperature it was left at. I usually leave it on auto all the time, because, well, it's automatic. On the rare occasion when I do manually adjust, I've also noticed that turning auto back on seems to always turn on the AC. I assume this is because it's needed to cool the air when it's hot, and to dehumidify when it's cold (or risk fogging up the inside). Not sure though.

[Beer Goggles]

I think the confusion is that it's adjusting the temp to the difference of what you want inside and what the temp IS inside. Not the outside air. So the closer it gets to the set temp inside slows the fan down.

factoring in the temp outside that doesn't matter to you on the inside it worthless.

[TeaRoy]

I'm not sure if my auto temp is working properly. I have an 08 328i and whenever i hit the AUTO temp button - the temp will turn on to the temp i left it off on - say if it's 25 degrees outside and i put it on let's say for example 70 the day before. When i turn on the AUTO shouldnt it be set to 84 degrees? Mine doesnt. Also, whenever i turn on auto, the fan goes all the way to full blast and the AC turns on. Is this normal or should i go into the dealership?

i remember when i first bought my car - it was warm outside and then it turned night and when i went into my car the temperature adjusted to the outside temp.

I think I know what you're saying and that's exactly how mine works - you're fine. It will stay at the temp you set. So if you set it at 70 degress last week and haven't touched it...it will stay there. When you hit 'auto' the AC (don't think cold) comes on, but it can still be heat - it's just 'conditioned' air. The outside temp doesn't matter. But, let's say it's 30 degrees in your car and you hit 'auto' and the auto setting you left it at is 70 degrees. As soon as the car warms up enough to pump warm air into your car, the fan will go full blast pumping that warm air into your car. The goal of 'auto' is to get it to the temp you selected the fastest way possible. As Beer Goggles said, once the inside temp gets closer to the goal...the fan slows down.

Hope this helps.

[AirPower]

I always wondered why the A/C light came on when I wanted the car to heat up. So that just "conditions" the air, it doesn't cool it. I always tap it off, I guess that's not necessary.

[mryakan]

I always wondered why the A/C light came on when I wanted the car to heat up. So that just "conditions" the air, it doesn't cool it. I always tap it off, I guess that's not necessary.
Actually even on cars without the auto climate control, most car manuals recommend that when you try to defog the car in the winter that you set the heat on max hot, fan full blast, and A/C on, until the windows defog then you can turn the A/C off. With your auto climate control, the car is doing the same thing for you. Auto means leave it alone, it knows what it is doing :D.

[rdadhania]

But, with the A/C on via the "auto" mode, are we losing fuel economy and power? Because thats typically what happens when the AC is on in the summer time. If that is the case, ill just tap that button off, but leave the rest of the system auto

[sor]

I don't think I've noticeably lost power/gas mileage from an AC since the old Pontiac 6000 I drove in highschool. They're pretty efficient these days.

[Beer Goggles]

I don't think I've noticeably lost power/gas mileage from an AC since the old Pontiac 6000 I drove in highschool. They're pretty efficient these days.

They have minimized the loss but it's still there. Thing is when you start to have lots of power you feel it less. Say you lose 10hp, in a car with 170hp it's a 17% loss. In a car with 300hp it's a 3% loss. Just a smaller loss, but still 10hp.

[mryakan]

But, with the A/C on via the "auto" mode, are we losing fuel economy and power? Because thats typically what happens when the AC is on in the summer time. If that is the case, ill just tap that button off, but leave the rest of the system auto
Yeah, but I assume it doesn't stay on for long, so the effects are inconsequential on fuel economy and as for power, if you need it and go WOT then the A/C compressor will adjust and steal less power. Don't get me wrong, if you want to shut it off, go right ahead. I am just saying it is probably not necessary. Try it and see, you can always go back to your old ways and tell us why.

[Beer Goggles]

For maximum power and efficiency the less power being used, the less belts, the less AC the better. You can't cheat physics.

And to show that actual testing is better than "I think" Car and Driver did an article on this.
http://www.caranddriver.com/reviews/hot_lists/high_performance/features_classic_cars/gas_pains_mileage_myths_and_misconceptions_feature/turn_off_your_air_conditioner_feature
AC reduces MPG and power.

[mryakan]

For maximum power and efficiency the less power being used, the less belts, the less AC the better. You can't cheat physics.

And to show that actual testing is better than "I think" Car and Driver did an article on this.
http://www.caranddriver.com/reviews/hot_lists/high_performance/features_classic_cars/gas_pains_mileage_myths_and_misconceptions_feature/turn_off_your_air_conditioner_feature
AC reduces MPG and power.

I am not arguing that, but if you are cruising on the highway, who cares about a few hps lost for a few seconds. I am assuming the A/C eventually shuts off after defogging, but since I don't have that feature I am not certain, you guys should say. If it stays on forever and is not needed, then yeah by all means shut it off, if for nothing else but reduce wear on the A/C components.

[sor]

For maximum power and efficiency the less power being used, the less belts, the less AC the better. You can't cheat physics.

And to show that actual testing is better than "I think" Car and Driver did an article on this.
http://www.caranddriver.com/reviews/hot_lists/high_performance/features_classic_cars/gas_pains_mileage_myths_and_misconceptions_feature/turn_off_your_air_conditioner_feature
AC reduces MPG and power. What, did they use a 90hp neon or something? Not much info in that article. Sure, I see the image but they don't really say jack about the test setup.


They have minimized the loss but it's still there. Thing is when you start to have lots of power you feel it less. Say you lose 10hp, in a car with 170hp it's a 17% loss. In a car with 300hp it's a 3% loss. Just a smaller loss, but still 10hp.I get the point, but 10hp? Really? I'd be surprised if most cars had A/C units that used more than 3-5hp. Sure, it's something, but as I mentioned it's not noticeable to me, personally.

Not that I'm super-versed in HVAC or anything, but I was also under the impression that the compressor itself only turns on when it senses that the coils aren't cold enough. Sort of an intermittent thing,which would kind of make it a moot point on freezing days.

[Beer Goggles]

What, did they use a 90hp neon or something? Not much info in that article. Sure, I see the image but they don't really say jack about the test setup.

I get the point, but 10hp? Really? I'd be surprised if most cars had A/C units that used more than 3-5hp. Sure, it's something, but as I mentioned it's not noticeable to me, personally.

Not that I'm super-versed in HVAC or anything, but I was also under the impression that the compressor itself only turns on when it senses that the coils aren't cold enough. Sort of an intermittent thing,which would kind of make it a moot point on freezing days.

Funny ...the car in the pic is a BMW.

I love when people on the internet can never believe people doing a test and providing results. It's much easier to argue in forum land. They show the loss of MPG which probably is a good estimate of power loss since they are directly related.

3-5hp at the wheel where measured is more than that at the crank. I wasn't saying you lose 100hp, as I mentioned it loses HP and loses MPG. The reason you can't "feel" it is with cars with TQ and power it's less of a percentage loss. Yes the AC is magnetic and disengages but they are still using power because of the belt. It's why the HP ratings have changed too, and why real race cars don't have AC, weight and power reduction.

And for those who didn't read they did a 2.5mile oval and cruised at 35,55,75 and recorded MPG.

They got a loss of 15%, 9.3%, and 6.8% which is 3.6mpg, 2.2 mpg, and 1.6 mpg losses which I based on my current 24mph reading.

So even if we don't "care" or "feel" it's still there and a loss.

[rdadhania]

If it stays on forever and is not needed, then yeah by all means shut it off, if for nothing else but reduce wear on the A/C components.

There is no way of telling how long the feature is on or off...the light always remains on...


Funny ...the car in the pic is a BMW.

I love when people on the internet can never believe people doing a test and providing results. It's much easier to argue in forum land. They show the loss of MPG which probably is a good estimate of power loss since they are directly related.

3-5hp at the wheel where measured is more than that at the crank. I wasn't saying you lose 100hp, as I mentioned it loses HP and loses MPG. The reason you can't "feel" it is with cars with TQ and power it's less of a percentage loss. Yes the AC is magnetic and disengages but they are still using power because of the belt. It's why the HP ratings have changed too, and why real race cars don't have AC, weight and power reduction.

And for those who didn't read they did a 2.5mile oval and cruised at 35,55,75 and recorded MPG.

They got a loss of 15%, 9.3%, and 6.8% which is 3.6mpg, 2.2 mpg, and 1.6 mpg losses which I based on my current 24mph reading.

So even if we don't "care" or "feel" it's still there and a loss.

VERY well put :buttrock +1

The power loss isn't what really concerns me...but if I could squeeze out a couple extra mpg, why not?

[mryakan]

There is no way of telling how long the feature is on or off...the light always remains on...

I see, well you always lose control with automated systems, at least they left you the option of overriding it manually.