I'm installing a new thermostat and the previous one did not have a C wire connected. Tracing in back to the HVAC, I can't see a C output connection? Based on the wiring diagram (and reading other posts), i'm guessing i need to connect it directly to the transformer and the brown wire? Not sure if that's best, but looking for outside help. Bottom line - where should i connect my C wire and how should i connect it? Thank you! [![enter image description here]]
You are correct
The brown wire from the transformer to the relays in your unit is indeed the C wire you're looking for -- you can cut it and splice it with a bog-standard wirenut, or use a piggyback tab terminal crimped on the end of what you're using for a C wire to make the connection at a device. There may even be a spare terminal connected to it but nothing else -- the wiring diagram on your unit has provisions for a C wire from the unit to an external compressor contactor.