Well, I just got around to disconnecting my G wire, and it didn’t help. My furnace fan keeps coming on a second time and runs for 15 seconds.
I would seriously consider buying a different brand of thermostat if it wasn’t for the fact that I already have many WYZE products and don’t want to have to monitor a whole new system. 
This makes no sense… without a G wire, the wyze cannot be controlling the fan in any way.
Makes no sense to me either! That would point to a problem with my furnace, I guess.
I’m almost tempted to remove the Wyze thermostat and hook up my old Honeywell thermostat and see if the problem still exists.
Btw, I called the company that many years ago installed my furnace and they said they don’t deal with “smart thermostats.”
My wyze thermostat is buggy in heat mode. For the last two years, occasionally and randomly, it will stop holding the heat.
If I turn the unit off in the app, wait 30 seconds or so, then turn it back on, it usually “fixes” itself. Occasionally, I’ll need to do the power down cycle multiple times, sometimes taking hours before it decides to resume heating my house.
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I’ve called an hvac guy and they don’t seem to have a clue. My unit is an older unit but I’m wondering if it’s some buggy setting I have in the app.
OH, and unrelated, the thermostat is showing off line over the last two days in the app.
Any help would be appreciated. I’ve called wyze multiple times last year and they were completely unhelpful.
Random issues are tricky. Do you know if it happens with any other thermostat, or just the wyze? It could be a bad relay on the wyze if it only happens with the wyze.
If it happens with other thermostats as well, or when jumped out, then it could be a failing high limit, fan motor, or fan capacitor… Could also be a sticky gas valve or bad solder joint on the furnace control board. There’s quite a list of possible causes that can cause a furnace to not heat.
Next time it happens, and just power cycling doesn’t fix it, you can try jumping R to W - if the furnace starts right up, then you can be pretty sure it’s the thermostat - if it doesn’t, then it’s an issue with the furnace.
I wish I could figure out why my furnace is coming back on for 15 seconds. I’ve called several HVAC specialists, but they all want $110+ just to come over and look at it. They’re not guaranteeing they’ll fix the problem, but they want the money anyway. No thanks.
I’m having the same issue but when I turn the heat off, the fan keeps running…it does the same thing on the cool setting. My unit is brand new and worked great with my nest thermostat. I do have my settings for the fan to be activated by the furnace only. Can someone help?
Have you read through the manual for your furnace yet? After the furnace shuts down and restarts in 15 seconds, how long does it run and is the burner firing or just the fan running? Did your furnace do this with the old thermostat?
I have high efficiency propane forced air unit, new in 2017 with the house, and after reading the manual I learned the control has dip switches to make adjustments for cooldown delay and duration as well as other parameters. If your fan is kicking on temporarily it could be the furnace doing what it’s setup to do.