My ruud was installed in 2015. The C wire (blue) is not connected at the thermostat. I looked in the air handler the brown c wire comes off the board appears to be connected only to the outside wire.

This is current thermostat wiring. The blue wire is behind the plate and is not connected.



And wiring diagram off the air handler.





Do i connect the same brown C wire to the blue air handler line too? Current connection looks similar to the second diagram in the first pic..... I see the bottom diagram has the brown c wire hooked to both inside and outside units.

Updated op.]

@zw17





I think you can see it. So the brown wire comes off that top plug on the board. It runs out and connects to the white wire on the red circle that runs to the red X which i believe goes to the outside unit. The green x is the line to the thermostat and you see the unused blue wire wrapped around it.

The board is on the left side of the first pic but give me a few and ill take the cover off.

@zw17

Brown wire is marked C on top.

Bottom plug says w1 then w2 then C ....C lines up with the brown but the black on the bottom doesn't line up with any marking

Follow the wiring diagram you posted.  That is all you need

https://i.ibb.co/7zVvMQ2/20240403-194808.jpg

Follow the wires  in   down  from  top left

The  hookup  from  wires left to right and from terminals top to bottom are  R, C, G,  W1, W2

Red  is 24V
C  is  transformer common
G  is green to activate  fan
W1 is  heat stage 1
W2 is  heat stage 2
If you have AC    there should be a yellow  fed through from the outdoor condensing unit, coming through  into the furnace and fed up to the stat to  fire up the  outdoor unit

I would NOT  assume that wire colors follow  up to the stat,  check them out  continuity, etc

EG  example:   We added   AC  to the neighbor's  son's house,  and  someone evidently, when building the house,  caught the  stat wire  on a  duct joint    and  yanked it, stripping and shorting 2 of the stat wires  to the duct and furnace ground.  I've forgotten what colors, but this was a 6 wire stat and we only needed 4,  so the stat is wired with incorrect  colors to get it to work.  The  stat wire is unaccessable  in parts of the house

Got it. TY for the responses.

Had to call honeywell because the T-stat was an amazon return and was registered to another account. But on the bright side, had no issues calling honeywell. CS picked up right away and was able to unregister the device for me.