Hello, I have a 156 1.8 MK1. I'm doing this Chris' carputer project.
1. netbook with SSD, modded: relay instead of power on switch, runs on a 12vdc to 12->24vdc convertor.
2. 8'' display + touch(without any frame)
3. arduino board
I am thinking about the A/D conversion, I will be doing this using Arduino. Using eLearn I've found that the E20(aux instr plug) uses this pinout:
1 - 12v IGN
2 - 12v BAT
3 - GND
4, 5 - +/- for fuel pump floater
9 - min temp(ECU)
10 - temp(sensor)
For fuel: I will send 5V on pin 4, and read the value I get on pin 5 using arduino. The value should be less than 5V. Take some "sample values" and build the corresponding range(0-63L)
For temperature: I found out measuring pin 10 to GND imed after starting engine would provide a voltage that rises with temperature displayed on analog gauge. I already wrote down some values for <50, 50, 75, 90. I just need to lower the voltage on this pin, max value should be bellow 5V so I don't fry arduino.
I don't know nothing about pin 9
Does the ECU read or write to this pin? What happens if I ignore it(no connection to it). I personally think, pin 9 is used for ECU to get engine temp in a custom format, so ECU will trigger fan pos 1 and fan pos 2 relays if over 90*C.
I hope this helps, and if Chris156 sees this post, he would be willing to reply if I got it wrong or not and also with some hints(maybe voltage values he got on the gauges).