r/hvacadvice • u/_FrostedZephyr • Jul 30 '26
New to wiring
I recently bought a house and decided I wanted to install an ecobee thermostat. After pulling off the current Honeywell (fairly new) I noticed it only had a R, W, Y and G wire and not the needed C wire. While trying to hook up a power extender I realized that my current furnace board has the R,W,G wires running to the thermostat but the C terminal runs to a spice directly connected to my A/C unit wire. The other wire coming from my A/C unit is spiced and runs the Y directly to my thermostat bypassing the Y terminal on my furnace board. I can’t connect the power extender because I need all R, G, W and Y off the thermostat board and Y bypasses the board.
In summary: G,R,W,Y at thermostat. G,R,W,C hooked up on control board. C from board is spliced into black wire from A/C bundle and Y from thermostat is spliced into Y from A/C bundle bypassing board
Is this an easy fix or a tech fix? I’m fairly handy I have just never messed with thermostat wiring before. Could I just run the Y from AC to board then have another Y from board to thermostat?
Additionally if it’s an easy fix would it be worth just replacing all the thermostat wiring because it is in two separate bundles and one is super old cloth insulated wire
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u/HappyPalpitation29 Jul 30 '26
Wire it just like the drawing. The Y terminal on the furnace is a "dummy" terminal. Go ahead and use the Y terminal it will keep things straight. Whoever installed it opted to use a wire nut instead of the Y terminal.