Jottle

So here's something I still have a bit of a hard time understanding. I have an 06 navi, and I get that when I hit auto, the hvac system controls the temperature setting that I choose. But when I navigate to the manual controls and make any changes, the auto light shuts off. So if I tell the system to make the fan controls bi-level, the auto light shuts off. Does that mean that the system is no longer maintaining the temperature I have it set at and just blowing outside untreated air through the bi-level vents? On that same note, if I hit "A/C on" and set the temp to 80, what happens?

Daveymcgav

I was confused about this also when I first bought the car. The system appears to maintain the temperature as best it can with the settings you choose, even with the auto light off. If you hit A/C on and set the temp to 80, I imagine that it will blow hot air out with the A/C running.

I think of the "Auto" light as more of a "Full Auto" light .

n3ok318

iTrader: (1)

i hate the factory AC

when i set 72 with fan speed 2, that means I want 72F with fan speed of 2, not any colder or hotter to maintain car's temp at 72

Jottle

Well that's exactly my question. It seems that you're saying that with "auto" off, the air will not stay at a constant 72 degrees. This would imply that the "auto" is never really off and is always regulating the interior temp accordingly.

aznboi2424

iTrader: (10)

in full auto, it controls the vents, vent speed, AC compressor and fresh/recirculated air.

in manual, you get to control all of that.

in both modes, the temperature is still maintained at what you set the temperature to be. its just that when you override the "auto controls" for any part of the system listed above, then it is no longer full auto.

but say if you decide to change the vent location, and only the vent location, the other areas of the system are still being controlled by the car.

Simba91102

MTLer

I've mentioned this before but has anyone noticed that the "FULL AUTO" light never comes on? Ive tried all the combinations and i can't get it to light.

LukeaTron

The only "combination" that should be required is poking the auto button. Maybe I don't understand what you're trying to do?

spoiledkari

Here's my question...when I push the auto button, my A/C comes on. Does it stay on the entire time the auto button is lit up or does it go off eventually?? The A/C even cpomes on when I want the temp to be 80. That's why I don't use the auto feature caus I don't want my A/C running all of the time.

micksTSX

running the A/C with heat is not bad per se as it lowers the humidity so the interior windows stay fog free; the only down side is slightly lower gas mileage.

jlukja

The A/C stays on in "auto" mode only until the system decides it doesn't need it any more. In "auto" all the functions are controlled automatically. If you make any adjustment after you put the system in "auto" then everything else except for your adjustment will be controlled automatically.

Jottle

I bet that even though the A/C light is on during auto control. It probably isn't running constantly, as some of the other posters have already suggested in this thread.

spoiledkari

Ok, so if I put it in auto and set it on 70 then shut the A/C off, the system will turn the fan up and down to maintain the 70 but it will never turn on the A/C?? But, if I leave the A/C on in full auto mode, the compressor will eventually shut itself off when it is no longer needed?? Am I understanding this correctly??
I hate the run the A/C compressor when it's not necessary, hence the reason that I just don't use the auto mode. Maybe I'll start using it if I can fully understand it.

jlukja

rb1

I don't think the A/C stays on anywhere near all the time on full auto -- it just runs as needed (to regulate temperature in the summer, and humidity in the winter).

Note that Honda A/C in particular should be run at least weekly, even in the winter, because otherwise the internal seals will dry and cause expensive long-term maintenance issues. This is probably true of other makes also, but my impression is that Honda's are especially finicky.

I turn my A/C off sometimes, but usually leave it on auto and just change the temperature.

DuckDodgers

Actually, as I understand the HVAC, when the Auto function is off, the system works like a conventional system, that is the selected temperature is the temperature at which air is delivered through the vents. The system in this mode ignores the interior temperature sensors and concentrates on delivering the air at the temperature requested...which may result in an increase/decrease/no change in the interior temperature.

spoiledkari

Sweet!! Thanks! I'm gonna use the auto feature from now on!
You learn something new everyday!

LukeaTron

This is incorrect. The system will always modulate the temperature of the air coming from the vents so as to get the cabin temperature (as the system perceives it) to be what you've set it to. As far as I know there's no way to cut this feedback out of the loop.

Jottle

Man I'm glad I brought this up. The manual is pretty vague in this respect, and it looks like we all don't have a good source to confirm this. To me it seems that when auto if off, the air comes out at the temperature you select regardless of cabin temperature. Anyone have a way to get to the bottom of this?

Jottle

That sounds reasonable, but where does it say that in the manual? This is the original problem I've been having. I just don't see any sort of confirmation in the literature.

Bigtimebooch

The key here is that we have what is called climate control. Climate control implies that there is some type of feedback loop and the HVAC system will try to hold to a certain temperature. The target temperature of the system is the one displayed on the dash. It is NOT the temperature of the air. This means that if you set the car temp to be 72F and its 80F outside, it will keep cooling the car until it reaches 72F. If it dips too far below this, it will actually begin heating until it reaches the target again.

Auto mode seems to decide the fan speed and vent configuration on its own based on your temperature (and maybe even the outside temperature). How it decides is beyond me...notice that it wont turn the fans on high when you first start the car in cold weather so you don't get blasted with cold air.

Manual mode allows you to control fan speed and vent configuration. As near as I can tell it still tries to hold to the target temperature. I find myself setting the temp to max or min when in manual mode so I never have figured out if it's still trying to hold to a target temperature.

I have found that it is best to find a target temperature you like and keep it in auto mode. Use the defrost button when you want to defrost and turn it off when the windows are clear. While it says the system is "on" it just means that it is monitoring the temperature and does not mean that the actual air conditioning is running at all times. Also, keep in mind that just because the AC is on, it doesn't necessarily mean you are cooling the air. It is air "conditioning" not cooling. All in all, throw out everything you used to know about car AC systems and pretend you are a moron that only knows how to set a temperature and you will be better off.

While we're on the oddities of AC systems, remember that you can defog windows fastest by using outside air rather than recirculating the air inside the car...even when it's raining. Notice that our cars will automatically switch to outside air when you hit the defrost button.

rb1

Yes, this is one of my favorite features.

Also, in hot summer months, the A/C starts with recirculate on, and then switches to fresh air only after the car cools off several minutes later. Also very cool.

I leave mine on full auto almost exclusively now, except for occasionally turning off the A/C when I know it's dry and cold outside.

DuckDodgers

OK, I blew it , it's "Semi-Automatic Mode" after you adjust something...but on the A/C off issue, the system will try but cannot lower the temperature below that of the outside air.

I went digging and found my confusion was with the wife's Oddy A/C which has a rear A/C with auto matching or manual modes...

rb1

I don't think the compressor runs much in auto mode if the outside temperature is below the temperature you have set. When it is cooler outside, it seems to run only briefly to control humidity.

You usually can tell when the A/C is running, especially if the car is idling at a traffic light (4-bangers have much lower torque/hp at idle than 6 or 8 cylinder cars, and hence the idle is rougher when the AC is on).

I used to feel much as you do, but my having had the car for a while is that the A/C runs when it needs to, and not when it doesn't...