Help with common wire for 3rd gen nest

First time posting in the forums but read many other threads like mine but wanted verification as I'm not super handy with electrical. I want to install a nest 3rd gen but read the possible issues of the power stealing it would do and want to just avoid that headache if possible. Upon removing tstat I only have a r and w wire with a unused g wire. My hopes are to use the g coming off my 3 wire as my c since its not being used anyway.

With the pictures below can I plug the g wire directly into the yellow Power In 24vac? I don't have a voltmeter at the moment.

Any help would be great!

 

Yes, you need a voltmeter/multimeter to figure this out as these Taco boards are not consistent with their configuration. Harbor Freight usually has a multi-meter cheap.
Follow this thread: https://www.doityourself.com/forum/t...hermostat.html

 

Thank you. Just because I'm unsure about what to exactly test, would I place positive lead on the yellow Power In wire? And my negative on what?

 

When on the AC scale positive and negative don't matter. Follow the step-by-step instructions provided by PJmax in post #4 of the link above.

 

Welcome to the forums.

On the 403.... the R is fused which leaves the yellow as C. Always good to check anyway.