I have no c wire at thermostat (5 wires at thermostat) No motherboard at hvac unit. 2 cables one from thermostat and one from outside unit. I have the google low power connector but can’t locate a common wire. I found small transformer in hvac that says com . But has 2 wires going to a white connector . Everything is wire capped and no colors match up at all. I am totally lost. In photos I have 2 brown cables the one on top goes to thermostat the bottom one goes to outside unit. And in photo that’s the white connector com wires from small transformer goes to. I have 1 thermostat dual system heat and cool
What is the model # of your system? It should be on the lefthand label just behind the thermostat cable connections in your last picture.
It looks like you don't have any spare wires in the thermostat cable that goes from the air handler to the furnace which means you'll need to replace the current cable with a new 18/7 thermostat cable or if that is not possible you can use the Google Nest Power Connector.
I'm going to guess that the C wire in the air handler is the blue wire with the wiring nut.
Yes, I think the C wire is the large blue wire connected to the smaller blue wire.
Here is a diagram showing how to wire the power connector. You only need the power connector if you don't have a spare wire going from the air handler to the thermostat. Just wire the yellow O/B wire straight through like the W and G wires are.
