Using Arduino to control car heater/ac controls

hello, new to forum here.

I purchased an Arduino Uno and a raspberry pi. I have a car that uses manual knobs and buttons to control the heater/ac/zones. The manual buttons and knob assembly connects to a wire harness, so its electrical and not mechanical.

I am putting and Ipad into the dash and the heater controls are in the way. Rather then relocate them like others have done, I would like to just get rid of them (or hide them for an emergency), and instead... have the ipad control the heater..makes sense right?

Now I have 2 scenarios worked out in my head..ideas really.

  1. I somehow find out the signals that the knobs are sending to the heater/ac/zone motors and I make the arduino replicate them. Then I can just attach the arduino to the wire-harness, and it will act as the buttons/knobs. The car ECU doesn't have to know at all. This is assuming the signals can be reproduced by the arduino (hoping they are just a different resistance for each position on the knobs).

  2. If this fails, I can maybe show the stock heater controls under a seat or dash...wire up various servos to the knobs, and then the arduino can control the servos, which in turn turn the knobs....tacky i know but may work...(issues im seeing, how do I have the servo turn the knob to position a, and stop...because the knobs turn to various positions and stay in that position..IE, low fan speed, low air, high heat....)

Then after that is all tackled, I already have DLed the arduino app for ipad..need to get that working. Trying to decide how to get that to work. Bluetooth is probably 2nd choice to using the Ipads docking cable... I did buy a seeenstudio motor control, works nice...however TAKES UP THE ENTIRE arduino....so in that case, how hell do i add a BT module? all pins are used up.

finally....raspberry pi comes into play....maybe that is better way to go? But I don't know anything about it(even less then arduino)

Well there you have it. open to any suggestions or comments, help and ideas welcome.

Thanks.

Obviously the first option would be much better than the second one, but the second option would be conceptually simple since you can command a servo to move to a given position and it will move there and stop - just what you want. The problem is all the hardware you need to build and get working reliably to have each mechanical control operated electronically - it seems like a fiddly job and I can't imagine it being very reliable. If you can figure out the interface, the electrical/electronic approach would be far better.