topic Nest thermostat - Fan-only option not working, tested in all modes, any thoughts? in Nest Thermostats

Nest thermostat - Fan-only option not working, tested in all modes, any thoughts?

brettgrodeck — Mon, 22 Apr 2024 20:35:48 GMT

I installed a Nest thermostat. The heating and cooling work fine. I want to be able to run the fan only. I live in a two-story condo, and the temperature differences between the floors are dramatic. Plus, I want to filter out allergens during spring.

I've scoured these pages for solutions. The fan-only option appears in the UI but doesn't run. I tried the fan-only setting in Heat, Cool, and Off modes. I tested all the equipment options, including heating, cooling, and fan. I updated the software and restarted it. The fan works fine when heating or cooling, just not by itself.

Now, I think the wiring is wrong. I know the fan worked with the old thermostat. Attached is a picture of the old wiring, the new wiring, and some settings. I'm willing to offer someone $100 to diagnose the problem! My objective is to run the fan independently of the heating and cooling.

Re: Nest thermostat - Fan-only option not working, tested in all modes, any thoughts?

teridr — Tue, 23 Apr 2024 03:41:48 GMT

I'm no expert, but I find it easier to start the fan from the home app on my phone. But I just figured out how to use it on the device itself. I labelled the pictures with instructions. Hopefully this helps.

1. First Screen3. Slide finger on side - heat should be first4. Slide finger on side to fan5. Slide to adjust time, Tap to move down to Start or Cancel2. Tap side for This screen to pop up

Re: Nest thermostat - Fan-only option not working, tested in all modes, any thoughts?

teridr — Tue, 23 Apr 2024 03:44:01 GMT

Not sure why the pictures are out of order. Follow the numbers 1-5 on my pictures. Hope it helps.

Re: Nest thermostat - Fan-only option not working, tested in all modes, any thoughts?

brettgrodeck — Wed, 24 Apr 2024 15:26:52 GMT

Thank you for posting this. Essentially, I've been following this same process. I always get to the point where the thermostat thinks the fan is on, and the fan icon spins, but the fan doesn't actually blow.

But, I really like your Nest interface. Very different than mine. It must be a newer model? Did you buy this recently?

Re: Nest thermostat - Fan-only option not working, tested in all modes, any thoughts?

brettgrodeck — Wed, 24 Apr 2024 15:31:23 GMT

I forgot to mention that I haven't yet tried turning on the fan using the phone app. It's not on my phone, so I'll wait until my other half gets home. If the fan works using the app, I'll report the results.

Re: Nest thermostat - Fan-only option not working, tested in all modes, any thoughts?

teridr — Thu, 25 Apr 2024 04:23:20 GMT

Thank you! The color is Sand. I ordered it in November and installed it in February 2024. I ran a new 8 wire from my furnace to the thermostat. Right now, it is only controlling the furnace (and fan). I use a swamp cooler in the summer. But I would eventually like to add a UV light and humidifier to my furnace and want to be ready for that (and if I ever switch to an air conditioner). In the old wiring, one of the wires was damaged somewhere in the wall (which was another reason I went ahead and ran a new set of wires). Because I DON'T have air conditioning, I don't have 2 of the wires connected (see pic). I know for me, connecting the Y (yellow) wire was causing issues, and I think it's because I don't have air conditioning.

I figured out how to use the Nest touchscreen when I was trying to see if I could help you. 😬 It's just so easy on the phone. I'd like to hear how you figure it out.