Hey everybody,
So I've had this idea for a while now, and I'd like to get us together to figure it out. I want to decode and document the climate control signals that come from the climate control button/display unit to the climate control computer, and make that information avaliable to everybody.
The reason why i want to do this is to give us more options for dash mounting things. Imagine, for example, how nice it would be to give the climate control a smaller display and fewer, smaller buttons, to free up that space for a few more gauges, without having to resort to things like blocking off vents or using up the cubby hole underneath the stereo. You could even move the controls elsewhere, freeing up that space for a nice large touchscreen for a carputer, dvd player, or gps unit. Ultimately, you could even write a computer program that provides the climate control buttons onscreen, eliminating the need for a separate control panel althogether, and providing a very nice factory-esque integration.
The possibilities are really endless, but even the simple ability to build a smaller controller to provide more room for gauges would be a boon.
At least, i think so, do you guys agree?
If so, lets work together to figure out the control scheme. I've pulled out my climate control unit to start playing with it, but I don't have an o'scope, so if anything ends up being beyond the abilities of a voltmeter (and a cheap one at that), I won't be able to do it all.
It would also be easier for someone who had an extra display and computer lying around, as I'd like to keep mine installed most of the time, so if any of you have those, get testing!
Anyway, i've been playing around with it today, and here's what i have found so far (on my 91 vr4):
There are two connectors on the back of the display/button panel (i'll just call it the panel from now on), one is 12 pins and one is 16 pins. With only the 12 pin connector connected, the display does not light up and the unit will not beep when buttons are pressed, but vents and fans respond to button presses as if everything is ok. In other words, the 12 pin connector is for the buttons, and by following traces I've found that the buttons are pretty much just hooked up directly to pins on the connector. I've found the two pins that connect the off button, for example, by following the traces, and I intend to do that for all the buttons.
The other connector (16 pins) seems to recieve signals from the climate control computer. When only the 16 pin connector is plugged in, the display lights up and correct climate control information is displayed, but no button presses have any effect.
This means a couple of things: First of all, it looks like no matter what it would be really easy to make a custom button set to control the thing. The stock buttons are large and take up a lot of space, and some are redundant. On the redundancy, for example, you don't need one switch for in pulling in outside air and one for recycling air, you could make that a button that toggles the two. Same with the ac/econ buttons. You could also remove the off and defrost buttons and make it so that pressing mode cycles through those options as well. Some of that would require a microcontroller, but it would be pretty simple, and if didn't want to consolidate switches, just use smaller ones, the hookup would be even easier.
Also, by looking at the control PCB, i can see that the only traces that go beyond the display are for the buttons. That means that if you made a new button panel or whatever, you could literally saw the sides off the PCB and just use the display, or drill holes in the pcb and mount the gauges directly in it, on either side of the display, assuming you find a place for your buttons. Sawing the sides off of the display would shrink the PCB from 9 inches wide to just 3.75" wide, giving you 5 1/4 inches of new space!
However, if we do figure out the interface for the display, we could eliminate that as well and replace it with a more compact display, with anything as small as a two digit temperature display and a couple of status LEDs, or anything you can think of.
So I'm gonna keep working on figuring out the button interface, and if any of you have some ideas on how to grab the signals from the climate control computer to the 16 pin connector, lets get that going too. For now though, I'm off to dinner and a party.
Oh, and
check out some pics of the insides of the unit and the newly created 9"x8.5" opening created when the climate control and stereo are removed.
-Taylor