Wiring issue with thermostat

I opened up the panel in the furnace to see what the wiring looked like before I attempted the install - see photo. On the thermostat side I only have red, yellow, white and green. No common “C” wire visible. Two questions:

  1. Why do I have two wires - red and yellow - into my yellow terminal? Do I leave the red one there if I need the c wire adapter?
  2. Since it looks like I have a common wire shouldn’t I see that at the thermostat? I guess it could be in the wall unused?

I have watched the install videos I just want to make sure I know what I am doing.

Call your ac guy before you blow up caps

It’s been fairly common that a currently unused at the thermostat wire, in this case your C wire is either wrapped around the cable inside the wall (ideally) or cut off right at the insulation sheath. If you have any slack behind your existing thermostat, I would look carefully to see if it’s there and you can get enough to wire the Wyze. I’m not sure about your yellow and red in the same terminal.

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The common and red Y wire go to your AC compressor outside.
The Red R wire, Green G wire, Yellow Y wire, and White W wire go to your thermostat.
To hook up the wyze, use the C adapter with the wires that go to the thermostat. Leave the red Y and white common on the furnace board.

Thank you I will give it a shot