HVAC Controls

[Iowa4Runner]

That is wrong. The same temp control for the auto controls the temp in manual mode.

Put it in manual and turn the temp up to 82 degrees and see how hot your truck gets.

It's not wrong, not in my 4Runner. If the temp setting was 75 all year long, the air coming out of the vents would be hot in the winter and cool in the summer. That's not direct control of the supply temp. In simpler, older car HVAC systems the cold-hot dial determined the temperature of the supplied air. In my opinion this conventional method is what our 4Runners should revert to when in manual mode.

 

[ToolmanJohn]

sensor under the ignition

There is a sensor inside of a slotted hole in the dash just below the ignition. If you shine a flashlight in there, it seems to be a thermistor. I think that is the sensor for interior air temperature.

 

[Iowa4Runner]

Re: sensor under the ignition

There is a sensor inside of a slotted hole in the dash just below the ignition. If you shine a flashlight in there, it seems to be a thermistor. I think that is the sensor for interior air temperature.

Yeah, I saw that when I took the panels off to do the MPG readout mod. The sensor is in what looks to be a rigid hose, that presumably leads to the inlet side of the blower.

 

[Cliff s]

The A/C auto system does have some querks. If the A/C is on auto
it always switches the fan to direct the air to your face. I sometimes
like to have the cold air to my feet. Then you have to be in manual.

I did find that if you set the fan on low and split between face and feet
and then set the temp control it will keep the cabin comfortable over
a very wide range.

One nice feature is the fan won't come on until the motor is warm
enough to make some heat.

I don't think that the auto function was very well thought out in its programming.

One trick I use frequently on hot days is when you first
start the motor open the rear window about 1/2 to let
the hot air out. When the cool air starts from the A/C you
can close the rear window.

Cliff s

 

[Bill42]

I guess it might be just what one is used to. I constantly had to turn up my manual system and then mess around to get it right on my previous car. Now, I just set the auto and the temp and for the most part forget about it. I really like it.

 

[00void]

my one major beef w/ the HVAC controls is thus::

if i want fresh air blowing in the cabin it'll do it (obviously). but let's say i want to make the temp. 80 from say 85. if the fan is OFF, i have to turn it ON just to adjust the temp. with my 2000 Sport w/ the radial controls i never had to do that. i guess it's not that big of a deal, but it can be a pain in butt driving 75mph and having to look down to adjust it. another beef is that i don't like the fact that in order to get air through the rear vents, the 'face' setting has to be selected. i liked the 3G w/ it's own fan settings.

i like when you hit auto in the winter it won't blow out cold air, but gradually build up the fan speed as warm air becomes available (like already mentioned).

also, i don't like how (mentioned again) if you set the temp to the coldest it automatically selects the recirculate setting for you.

one cool thing though i also like (and this may be common knowledge) is when i have the fan off, but have air coming in, if i want to have the air stop, rather than directing it to say my feet, i just hit the recirculate setting and it stops any air from entering into the cabin.

 

[MicaBlue03]

Auto-recirculate function

I get along ok with the system, usually in manual mode. I live in a moderate climate and don't need A/C too much of the time, so I prefer not to have on unless necessary (drag, compressor wear, etc.)

One thing I dislike is how it uses the exterior air temp sensor to automatically turn on the recirculate function. Unless I'm doing significant A/C, I like to leave the system on fresh air, and when it's the slightest bit warm out, it automatically switches to recirculate mode.

There are many situations around here on cool but sunny days where the inside gets warm by the end of the work day (greenhouse effect) and all I really need is to turn the fan on; no A/C. But the system has automatically switched to recirculate, and the fan won't do any good just recirculating warm cabin air. In manual mode, I'd like the system to be really manual, not automatically making ANY changes for me.

 

[Koz]

Problem 1. The HVAC control system adjusts the supply temp (the air that blows out the vents) to keep the sensed cabin temperature at the temp setpoint you select. In manual mode you should be able to have the control loop control for supply temp instead of cabin temp. That would be more like the traditional manual control, which I like.

Problem 2. If you start off with the temp set at 70 (or whatever) and later decide to drop the temp setting to "lo", the system switches to recirc, even when it's 50 deg. outside. That is just plain idiotic.

1. You can control the vent temp by adjusting the cabin temp. On a manual system you have a control to adjust the fan speed, direction/vents/location, and the temp of the air. You have all of the same controls in the 4Runner. There is a button for each fan speed, you have a button to select which vent/direction, and you can set the temp by pushing the up/down temp button (with the digital read out). They all can be set independently just like a completely manual system.

2. The reason the system changes to recirc is because you are telling the system to cool more but have lowered the fan speed. The system decides that to achieve the desired (lower) temp with the slow fan speed it's probably defaulted to use only cabin air. This is a faster way to achieve cooler cabin temp in the summer. This is what I was talking about; you will get lower temp faster by cooling cabin air that has already been cooled compared to outside (warmer/hot summer) air.

I've never had to cool yet, since I got the truck in Feb. This weekend I will probably get the first chance to see how it works. This will give me better idea of how to set the heating /cooling controls to achieve the desired effect. As far as heating, I like the way the system is designed to work.

Koz

 

[Iowa4Runner]

1. You can control the vent temp by adjusting the cabin temp. On a manual system you have a control to adjust the fan speed, direction/vents/location, and the temp of the air. You have all of the same controls in the 4Runner. There is a button for each fan speed, you have a button to select which vent/direction, and you can set the temp by pushing the up/down temp button (with the digital read out). They all can be set independently just like a completely manual system.

2. The reason the system changes to recirc is because you are telling the system to cool more but have lowered the fan speed.
The system decides that to achieve the desired (lower) temp with the slow fan speed it's probably defaulted to use only cabin air. This is a faster way to achieve cooler cabin temp in the summer. This is what I was talking about; you will get lower temp faster by cooling cabin air that has already been cooled compared to outside (warmer/hot summer) air.

I've never had to cool yet, since I got the truck in Feb. This weekend I will probably get the first chance to see how it works. This will give me better idea of how to set the heating /cooling controls to achieve the desired effect. As far heating, I like the way the system is designed to work.

Koz

Koz we're on different pages here. I don't feel like hashing out the details, so just trust me when I say that Toyota needs to make a few improvements. I'm not just making this up... I worked for Siemens Building Technologies for 5 years and most of my time was spent writing control code for, and testing, HVAC systems... I'm going to go out on a limb here and bill myself as the HVAC controls expert of the board...

 

[Koz]

Koz we're on different pages here. I don't feel like hashing out the details, so just trust me when I say that Toyota needs to make a few improvements. I'm not just making this up... I worked for Siemens Building Technologies for 5 years and most of my time was spent writing control code for, and testing, HVAC systems... I'm going to go out on a limb here and bill myself as the HVAC controls expert of the board...

I'm sorry I didn't realize you being the HVAC expert you are, I was just trying to help!

Koz

 

[Iowa4Runner]

I'm sorry I didn't realize you being the HVAC expert you are, I was just trying to help!

Koz

Hey no apologies necessary, I understand where you're coming from. I was just being lazy by not making more of an effort to clearly communicate my thoughts...