HVAC Data stream, information from my digital storage Scope.  This stream transmits temperature, Vent position and diagnostic data only.
OEM HVAC PCB connections - Needed for external interfacing 
NOTE: Wire Colours are ones I used in my prototype. Encoder Pin numbers refer to the OEM Encoder pin designation on the PCB - that part of the PCB has now been cut off. 

With this Circuit the HVAC is now fully controlled via:

1: A small remote control device that can be wired or plugged into the 4 wires coming from the modified HVAC board (Or a low cost Wireless link = No wire conections).

2: Software on a PC with full touch screen control and display of everyl HVAC function. 

3: Both 1 & 2.

All firmware for the microprocessor interfaces is free and will be posted here soon.          
Modifying the HVAC - Dual Zone Climate control PCB
On the Left:

Rough idea of how hard the HVAC interface micro PCB is to make.

Note: The sockets along each edge are not needed.
Microprocessor interface circuit: 

All parts are low cost and easily available, most from Jaycar. Only 4 connections leave the modified case - Serial Data TX & RX, +12v and Ground. If a USB to serial cable or module is used (for Computer control) then an optional 5v from the USB line is used.
REMOTE interface circuit: 

All parts are low cost and easily available, most from Jaycar. Only 4 connections leave the modified case - Serial Data TX & RX, +12v and Ground. If a USB to serial cable or module is used (for Computer control) then an optional 5v from the USB line is used.
A picture of the Remote board, I had an old Arudino Shield that I used for the LCD display. HVAC switches and 5 LEDS are simply connected to the sockets on the PCB.  Once again just a few resistors and a 5v regulator.

Could not get a good picture of the display.