SOLVED: No power getting to the thermostat

dougrainer wrote:
1. You have NOT removed all the wires from the hole for the Tstat.
2. You will NOT have "blue" wires at the tstat. The Blue wires are the 2 just for the furnace AT the furnace that go to the wall tstat and return
3. Most OEM's use standard home type Tstat multistrand wire to connect the Roof AC and to the furnace.
4. Usually they use the small 20 gauge wires---red and white to go from the furnace to the wall tstat.
5. When you have your type tstat, the one blue wire at the furnace that is 12 volt, it goes to the Roof AC control board in the AC. THAT wire is what supplies 12 volt power to the Roof AC control board and then DOWN to the wall tstsat. On other models, the blue 12 v wire goes to the wall tstat and then another wire then feeds the Roof AC for 12 volt power to the Roof AC. You need to get all the wires out of that small hole in the wall and odds are you will see a wire not connected. Doug

Thanks Doug. The thermostat wiring shown in the above pic is the way it's always been. I've looked at it before and made notes about the wires and colors. If I look further in the wall hole, I can also see a black wire, and that one additional red wire that has a wire nut on it (with a very small gauge red wire connected to it).

Here's my AC control box..



I cleaned up these connections when I first noticed the problem a couple days ago. From left-to-right, the colors are yellow (Y), gray (GL), green (GH), and blue/white connected together (B).

Based on what you're seeing, what would you check next?