I had the extra wire in the wires run from my thermostat to my A/C, but the old thermostat did not need the C wire, so it was cut and stuff on both ends. While installing the new thermostat I realized that a C wire is needed, so I pulled out the stuff wire in the wall and attached it to the C on the thermostat. Went down stairs, opened the A/C unit and found that there isn't a C connection on the board. There is a W, R and G and it appears the Y goes out to the A/C compressor outside. My question is, am I able to cut one of the wires from the transformer on the 24v side that I think is the common side, it's grounded, and simply use a wire nut to connect everything back together while splicing in the wire that was unused, now making it the C wire? here is a picture. I was going to cut 1 of the 3 blue wires. It's hard to see in the pic, but there are 3 square terminals on the blue side that 3 wires attach to. Please help and thank you =) http://i.imgur.com/Hk0US7J.jpg
side note, only terminals on the a/c board are W, R and G. The yellow wire doesn't even attach to the board, but connects to another wire that looks like it runs out to my a/c compressor outside.