Prepare for a silly question, but I actually have no idea whether this will work...
The scenario:
I am building a "restomod" restored classic car, and I'm currently in the process of looking at the HVAC system. I have bought a new air conditioning system from a company called Restomod Air, and it comes with a nice little heat exchanger with solenoid controlled valves and a fan and some other nice bits. As standard, it comes with a set of controls comprises of 3 10k potentiometers which each take a 5v reference signal from the little ECU box that comes with it, and turning the pots returns a 0-5v signal to the ECU for 3 functions (fan speed, temperature and vent position).
I don't want to use these controls though, because I have an existing set that come with the car. These controls have a rotary control also, and are also based around a 5v reference signal and a 10k potentiometer which returns a 0-5v signal. The 5v signal is this time produced by a 5v regulator on a small PCB attached to the back of the control plate. To show the position of the pot, 10 LEDs sit around each pot and used to be controlled by a dashboard ECU which I have now replaced with an arduino controlled dash pod which handled the instrument cluster functions as well as the lighting of these LEDs as required based on reading of the 0-5v signal output by the plate.
The proposal:
What I would like to try to do, is take the 0-5v signal I already have from my new dash pod for each control, and plug it directly into the signal pin on the new air con ECU. This means I'm ignoring the 5v reference signal coming from the new ECU and instead bringing across a 5v signal from a different source.
Of course both the ECU and the switch plate are plugged into the same power distribution system, so they ground to the same location. So will this work? My brain says yes, but I'm not 100%...
I'm sure he'd love this project, I'm getting right into the details..!