Thanks, but this is not a normal HVAC, it is an in-window swamp cooler with a very simple 3-button remote. I am guessing the commands are PWM encoded so I can use a RasbPi to read them then emulate them. From what I have learned, the Arduino may not be fast enough for PWM frequencies required, so Pi it is.
My boat is floating fine. Using the hacked-remote approach is just adding in more things to go wrong. Reading and emulating it all with the one device makes for a tidy approach. And, decoding the IR is not that big a deal as I have the equipment to do it.
IF I wanted get really simple I could use RC-servos to push the buttons on the current remote. But again, I want to automate this all and that would just make a bigger mess. Keeping it all on the one processor board system, just makes more sense to me.
I don't have an Arduino, (I was going to buy one for this project, but I always research well before buying anything) but do have a Pi so I will use it.
I may buy an Arduino just to play with after this is working, but for now it looks like the Pi will be an easier approach.