3rd gen nest thermostat “heating” but furnace not turning on

[Msnyder]

Hi community- I’m new to posting but have been an avid Nest/Google product user for years. Recently, somewhat out of the blue (we’ve had the same thermostat in 2 different houses over the last 6 years), we started having heat issues. We noticed the house was cold when we’d wake up (heat set to 70 but temps would be around 64 in the middle of night/morning). Had an HVAC tech diagnose and replace our furnace control board and gas sensor. “Fixed” the issue for about a week and started happening again. HVAC tech came back out and cleaned a dirty flame sensor and performed a PM and confirmed the furnace should be functioning properly (of course it fires up on command when they’re here).

Past few days, I’ve noticed the thermostat  and app both are orange and reading “heating” but the furnace isn’t on and temps continue to drop. Im thinking this is a Nest thermostat issue vs furnace/hardware issue. I’ve scoured numerous blog posts from other users and their solutions  (I.e. users needing to drop set temps to kick heat on and gradually adjust temps up, needing to manually restart furnace, etc). I can’t unfortunately babysit the app at night and adjust the temps manually.

Hoping someone out there can help or offer solutions. I’m tired of worrying about the temps in the middle of the night and whether my 1 year old is cold or not. Thanks in advance.

[Emmasz]

We’ve been having the same issue with our nest the last week or so with no resolution. It looks like there are a few others in the forum that are facing a similar problem as well. 
I, unfortunately do not have a solution right now, but you’re not the only one. Will come back to this forum if we find any more info! 

[Msnyder]

Yea, it's incredibly frustrating. Somewhat comforting to know that we're not the only ones but frustrating nonetheless. I'll pop back with add'l info if it comes my way as well

[Emmasz]

Update: we also had an HVAC person come out and our entire furnace needs to be replaced 🙃 so it seems the nest was not the issue for us. However, I have seen *multiple* reports of the same issue from people with Nest thermostats, so I do believe there is a software glitch or issue that Nest needs to patch. Hoping you find a resolution soon!

[CoolingWizard]

@Emmasz 

what was the very specific reason that that company told you that your furnace needed to be replaced? Many companies try to force consumers to replace old units so they can make more money even though they don’t have a defective system. 

AC Cooling Wizard

[CoolingWizard]

in order to diagnose this particular problem most accurately you need to have a multimeter and when the thermostat is orange and saying it’s calling for heat and you’re not getting any heat, you need to go to the furnace and measure the electrical current between common W1. if you find there’s voltage there, the thermostat is indeed calling for heat.  if there is no voltage showing up there and the display is orange, this is definitely a problem with the nest. Thermostat.  
keep in mind with gas furnaces when you take the cover off in order to check the voltage on the wires you will open up the power safety switch, which kills the power to the furnace. Make sure you know what you’re doing before you start this check

AC Cooling Wizard

[Msnyder]

Thanks coolingwizard. I’m comfortable enough to work my way around the control board but never measured the current to the board. If you recommend any videos on YouTube or articles I can read, I’d appreciate it. I’ll poke around myself but would take any suggestions you have. Thanks again