Hi. I have a heating/cooling system with four wires. The Nest works fine in single stage mode with Rh, G, Y, and W1. However, my furnace has two stage capacity and I would like to use it. As pulling a new W2 wire will be almost impossible, I decided to try the Add A Wire solution. I used the Add a Wire to add the extra W2 line I need. However, the Nest keeps telling me that there is no power to the Rh connector, which is not true as it’s clearly connected.
My hypothesis is that multiplexing the G and Y (which is what the Add a wire does) has broken the return to the furnace for the Rh power, as there is no C wire. How can I solve this?
Of course a fix would be to add a C wire, but as I only have four wires I can’t add a C wire AND the W2 wire I need using the Add a wire - I can only add one of them.
Any workarounds to get that power back to the Nest? Is there a way to use one of the other wires to get the 24v return happening?
thanks
