Confirm Light Sensor in IV or below?

[RRxing]

I have a IV (with no options) and was also curious about the "button" on the dash near the windshield. Here's some information from the Air Conditioning section of the New Car Features that I downloaded from the TIS that may explain it:

Compressor Speed Control
The air conditioning amplifier assembly calculates the target speed of the compressor based on the target evaporator temperature (which is calculated by the temperature control switch, room temperature sensor, ambient temperature sensor, and automatic light control sensor) and the actual evaporator temperature that is detected by the evaporator temperature sensor in order to control the compressor speed.

The air conditioning amplifier assembly calculates the target evaporator temperature, which includes corrections based on the temperature control switch, room temperature sensor, ambient temperature sensor, automatic light control sensor, and evaporator temperature sensor. Accordingly, the air conditioning amplifier assembly controls the compressor speed to an extent that would not inhibit the proper cooling performance or defogging performance.

Apparently, the sensor on the dash is used as part of the neural network that controls the air conditioning. Yes, I said neural network. That's also mentioned elsewhere in the section on air conditioning. Pretty damn advanced, if I do say so myself.

[RRxing]

Found it!

(b) Neural Network Control

(1) Previously, in automatic air conditioning systems without neural network control, the air conditioning amplifier determined the required outlet air temperature and blower air volume in accordance with the calculation formula that has been obtained based on information received from the sensors. However, because the senses of a person are rather complex, a given temperature is sensed differently, depending on the environment in which the person is situated. For example, a given amount of solar radiation can feel comfortably warm in a cold climate, or extremely uncomfortable in a hot climate. Therefore, as a technique for effecting a higher level of control, a neural network has been adopted in the automatic air conditioning system. With this technique, the data that has been collected under varying environmental conditions is stored in the air conditioning amplifier. The air conditioning amplifier can then effect control to provide enhanced air conditioning comfort.

(2) The neural network control consists of neurons in the input layer, intermediate layer, and output layer. The input layer neurons process the input data of the ambient temperature, the amount of sunlight, and the room temperature based on the outputs of the switches and sensors, and output them to the intermediate layer neurons. Based on this data, the intermediate layer neurons adjust the strength of the links among the neurons. The sum of these is then calculated by the output layer neurons in the form of the required outlet temperature, solar correction, target airflow volume, and outlet mode control volume. Accordingly, the air conditioning amplifier controls the servo motors and blower with fan motor sub-assembly in accordance with the control volumes that have been calculated by the neural network control.

[tumbleweed]

Wow! thanks for posting that RRxing, the system is rather more complex than I had imagined.

[jayvee]

Thanks RRxing!!

That is great info, and really interesting! It sure sounds as though the sensor should be there, unless the ECU for US models is programmed to NOT use light sensor data.

I'll need to verify the existing stalk connector harness, but it sounds as though I may just be able to switch out the headlight switch stalk to add "Auto" headlight control. Now THAT would be great!

The only last gotchas would be if the US and Canada ECUs are different, or if it requires a Techstream "turn on" of the feature by the dealer.

Anyone happen to know if the US and Canada ECUs are different?

It also would still be nice to hear from anyone who has actually disassembled their IV dashboard and can truly verify whether the light sensor is there, and connected. But RRxing's post suggests it should be.

J

[stream]

Originally Posted by jayvee

Thanks stream,

But doesn't your headlight stalk in your V have an "Auto" position? If so, what does it do? Isn't that auto on/off? My IV stalk doesn't have the "Auto" position, but I do have the auto-off as you describe. Do you have a stalk that has the fog light switch (which I dont have on my IV) but still no "Auto" position?

J

Yes--fog light switch. No--auto headlight position.

[RRxing]

Now, if someone has the time, patience, and inclination to download the electrical wiring diagrams for the AC, we can probably put this to rest. Until then, this is the only diagram I have:

[jayvee]

Here are snapshots of the AC and Auto light control wiring. RRxing is absolutely correct - there is a signal coming from the auto light control sensor to the A/C amplifier.

I've decided to perhaps try to tap into the wiring harness one of these days, and simply ground the "Auto" headlight switch lead (white) to see if it activates Auto headlights. I will post if I do.

Thanks all!

J

[jayvee]

Originally Posted by jayvee

I've decided to perhaps try to tap into the wiring harness one of these days, and simply ground the "Auto" headlight switch lead (white) to see if it activates Auto headlights. I will post if I do.

Tried this last night. There is a signal there, but not what it is supposed to look like, and when grounded, has no apparent effect on the headlights.

I also found out the that the Canada ECU (with true auto on/off headlights) is indeed a different part number, so probably is programmed differently too. If I had gotten this to work, I was intending to replace my headlight stalk with a Canada stalk, which has the "Auto" position. Unfortunately, I also discovered that the Canadian headlight stalk is on the RIGHT! (never knew that - I wonder why?)

So it's back to the drawing board......

[rachaelseven]

Originally Posted by jayvee

So it's back to the drawing board......

Do you think we could at least utilize the sensor to avoid having to locate a second sensor somewhere else?

[jayvee]

Originally Posted by rachaelseven

Do you think we could at least utilize the sensor to avoid having to locate a second sensor somewhere else?

I don't know - without knowing exactly what the sensor is supposed to provide to the ECU, or what the aftermarket kit requires for a signal input from the sensor, I'm not sure how to utilize it. But if you were able to ue it, you'd need to tap into either the ECU connector wiring (not too tough, L7 is relatively easy to get to) or at the sensor itself, removing the entire dash top, and at that point I think you might as well install the sensor that comes with the aftermarket kit.

I was watching the ECU pin input (that gets grounded by the "Auto" stalk swith in Canada) with an oscilloscope as I varied the "daylight" from pitch black to very bright (with a flashlight) and I didn't see any change in the signal. I think it's supposed to be a square wave pulse that gets narrower with increasing light (the repair manual isn't completely clear on this), but I was seeing a sawtooth wave, and no changes. (But I wasn't looking at the sensor output pin (L7-21), which is also supposed to be a pulse signal. Maybe I'll do that next time I have the instrument panel off.) So the ECU doesn't appear to be providing the signal at the switch pin that it does for Canada. Might be an ECU programming difference between US and Canada.

If I discover any more on this, I'll be sure to share it. I was pretty bummed about not using the factory auto stalk and circuit....and then the whole right vs. left stalk thing.

But hawkmoon looks like he found pretty good alternative, and I still have two switch blanks left, if I use the "ebay" fog light kit (which I've ordered, as well as the fog covers). I might see if I can find another "yaris" plug switch with a different symbol, to use for the auto lights, if I want to "switch" that function in. Might be able to trace the switch manufacturer by info printed/molded on the switch.