# Issue with Nest



## cultrosj (3 mo ago)

the original thermostat was an old Honeywell mercury round unit- 4 wires- red, green, yellow, black.

I installed a new nest using these wires, black wire into the W terminal- when the heat would turn on the fan would kick on but the furnace wouldn't, any thoughts? I've included pictures of the old Honeywell unit as well as the circuit board on the furnace


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