I've been having issues like the heat pump not heating. Now that it's hot outside, my A/C isn't working. Can someone tell me if my Nest thermostat is even wired correctly?




If it helps any, here is how the original one was wired and it worked just fine.


  • Those are the outside heat pump connections, the thermostat will be connected to a control module, usually on or next to the indoor vent/heat unit.
    – Stavr00
    Commented Apr 13, 2018 at 17:26
  • @Stavr00 I have a crawl space so I got under the house and looked at the furnace but didn't find any wires. I also traced the wires running from the outside unit, into the house, and they don't appear to be running with the other piping. I don't know if they go up the walls? I guess I don't know what I'm looking for. There are two panels on my furnace, the switches/breakers, and the filter access panel.
    – hack3rfx
    Commented Apr 13, 2018 at 17:33

1 Answer 1


Here are things to check first: - Check the 220V breaker serving the heat pump. - Check the over-pressure valve breaker on the heat pump.

  • No breakers seem to be thrown. When I turn the A/C on, it does blow air out. It's just not cold. My heat works too, or at least my AUX heat does. Heat pump is questionable in performance. Also, I don't know where the pressure valve breaker is at. I looked at the switches on the furnace under the house, they're both ON. There's a box attached to the side of my house, which has a big wire loom running into the outside unit. It just has a black pull-type lever in it. Not sure if that's what I'm looking for. Or, is the pressure breaker inside the outdoor unit?
    – hack3rfx
    Commented Apr 13, 2018 at 17:51
  • You can try to jump R to Y on the heat pump unit to see if it'll turn on (careful not to get sliced by the fan blade!) Leave it on for a few seconds. but don't do it repeatedly or you risk burning out the compressor.
    – Stavr00
    Commented Apr 13, 2018 at 18:29

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