Wyze Thermostat - Fan won't turn on manually

Just installed my new Wyze Thermostat yesterday. All wires seem to be connected properly. The testing process worked fine: heat came on, cool came on. The issue I’m having is that I cannot get the fan (on its own) to turn on manually under “controls”. Any ideas from the community? Thanks!

Is G attached to anything at the furnace/ air handler?

Yes @speadie , the green wire is connected to G at the furnace board. Not sure if it has anything to do with the currently programmed temps, but I would think not - that if you manually set the fan to “on”, it should blow regardless of temp settings.

Did your old thermostat have manual fan control (Trying to determine if the wire might be broken somewhere)

The old thermostat did have manual fan control capability, BUT no G wire was not connected since the old t’stat only had 3 wires. I’ve since ran a new 5-wire cable and all wires are connected at the proper slots on the furnace, and (I hope) on the new Wyze t’stat panel.

Please show the wiring at the furnace and at the wyze and at the old thermostat if you have pictures of it.

Here you go, @speadie. Thanks in advance!

Hmm. If you have an extra wire and an extra 3 amp blade automotive style fuse, you can try unplugging the thermostat and jumping R to G at the furnace. if the fan starts up, then there is a problem with the G wire in the thermostat run. If it does not, then your furnace will not run the fan without heat or cool being on. There may be a jumper or dip switch that controls this setting on your furnace board somewhere, you would need the manual for your furnace to determine the proper setting.

To be clear, you’ve told the wyze that you are not using the C wire adapter, correct?

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I’ll try your suggestion. Thanks, @speadie!

I would look at the furnace wiring diagram and make sure your wiring is compatible. Furnace fans are usually controlled by the temperature of the furnace, not by a thermostat on your house wall. But yes, there is a manual override often for cooling in the summer. I would expect to see a thermostate switch in the furnace box temperature and a connection set up that goes around that control for summer use. And that summer use circuit would be a seperate wiring in the wall thermostat. I still use an old Honeywell thermostat, It has a cooling cycle that is generally not used in our cool west coast climate.

Thanks for the tip, @billfern. Will look into this.

Yes, often furnaces operate independently of the thermostat except for that initial trigger on and a trigger off, but the furnace fan keeps right on running until the furnace itself cools down. Makes sense, you get all the available heat out of the furnace before it shuts off. And you might notice that when the thermostat comes on, the furnace fan does not start until the furnace heats up. The thermostat controls the flame in the furnace, or whatever you are “burning” as a heat source. It may not control much else. Often the thermostat turns off the furnace before the home is fully heated because it “knows” the leftover heat in the furnace will be sufficient to heat the house to the desired temperature. This is often a controllable feature of a thermostat on manual thermostats. I don’t use a smart thermostat yet, looking into it, but when I hear that the smart thermostats “learn” to do the job correctly, I believe the smart thermostat is looking at the overshoot from the temperature setting and learning when it should turn off the flame. The smart thermostat is obviously learning other things too. Understanding the working and interplay between the thermostat on your wall and the furnace is fundamental to making sure your thermostat is working properly. The thermostat doesn’t control the whole cycle necessarily.

I have a gas fireplace that seems to run as noted above. The flame shuts off a bit before the setting and the overshoot from the desired temperature is accounted for. But I have an identical fireplace in another room, seems the fan is controlled by a timer and nothing to do with temperature. If this fireplace has been off all night, and I turn It on in the morning, the fan starts up immediately as though it was on a timer that hadn’t finished when I shut it off the night before. Someday I will try to figure that one out. But it is not inconceivable that some furnaces might work like that too.