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Original Poster: Robert McElroy 8064
I have two Nest thermostats, "upstairs" and "downstairs". They have been installed and working perfectly for a few years. I recently had a power surge at my house, and it fried my downstairs AC unit (transformer + main board had to be replaced). After the AC unit was repaired, the Nest thermostat now gives me a Y1 wire power error (E30), and will not work. If I plug in an older (dumb?) thermostat, the system works fine. I tried swapping the "upstairs" and the "downstairs" thermostats just to see what would happen, and I get the same results downstairs... I am at a loss...
The downstairs system has gas heat, and uses wires RC, W, Y, G.
