Nest Help


So I recently purchased and installed a Nest E to replace my TopTech W955WH thermostat (our gas company was offering discounts and this is the last “smart” device that we have left to replace in our home). My furnace and A/C worked perfectly before: heat heated the house and A/C ran nice and cool. Our TopTech thermostat was powered by a black and red wire that was fed off of our furnace’s main board but in our basement we had a Pro1 Base Module hooked up with the actual thermostat colored wires that transmitted signals wirelessly to the actual TopTech thermostat in our living room. I knew that I couldn’t power my Nest E with the black and red wire so I ran a new thermostat wire down from the thermostat was in the living room to the furnace main board. I wired the furnace board the exact same as it was prior and when the Nest E was installed I wired it using the wire diagram that Nest had provided over customer service chat. The Nest E worked fine as far as it’s actual functionalities, no errors or anything, but when it was turned on “Cool” the furnace fan would turn on but the outside A/C unit would not. With heat, the furnace fan would turn on and then the heat would turn on as well, as it did prior to the Nest. Nest sent a replacement Nest E and before I go ahead on touch this new unit I figured I would ask the internet for help.

Also, we had a humidifier that we disconnected due to the unit being broken. The red and white wires coming from the brown sleeves are for that unit.

Thanks everyone!

Original furnace main board wiring:

Wireless module wiring:

New furnace board wiring after installing new wire (no dehumidifier anymore)

How Nest wanted me to wire up the Nest E (works with heat, no A/C)


Oh FFS, I forgot to reconnect the god damn A/C compressor power…



I had a similar problem with the Ecobee 3 lite. I spent a few hours trying to figure out what was wrong and why the unit outside wouldn’t turn on. I had an aha moment and realized the Y wires were backwards :unamused:


Had the EXACT same thing when I hooked up my Ecobee 3.

Was a fun surprise to think the AC was on the first hot day a month ago, and then came home to it just as hot as when we left.

In my case I was thinking that the tstat told the furnace to “go” and the furnace told the ac compressor to “go”. Nope.