Forum Discussion
Chris_Bryant
Jun 02, 2017Explorer II
OK- the blue wire is the thermostat wire, it will not have power unless the thermostat is getting power and calling for heat. You need to measure the red wire, and the power on both sides of the breaker in the furnace.
The black wire likely hooks to the furnace outside and the left (looking from the outside), and from there goes to the breaker.

The black wire likely hooks to the furnace outside and the left (looking from the outside), and from there goes to the breaker.

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