FYI - I took the updates and did all of these steps and still didn’t have the “by furnace” option. I chose LP and forced air and never got the option. Deleted the thermostat and added it back as Gas and forced air and now I have the option. Going to leave it like this as Natural Gas and LP should function the same.
Mine is old and not smart enough to override the thermostat, it’s probably all analog control.
Without the Wyze thermostat the fan is delayed, not sure if it’s a temp sensor or a preset time delay, but the fan doesn’t come on with the burner until the furnace is heated up. Also on mine after the furnace finishes the heating cycle and everything shuts off, the furnace kicks the fan on about 30 seconds later and runs it for maybe another 30 seconds to purge residual heat from the heat exchanger.
With the Wyze thermostat the thermostat, since the furnace is analog just sees a green wire fan signal, overrides the furnace, and runs the fan immediately.
Raym64, it seems that you either haven’t updated the firmware & app yet, or you don’t have it set right. This was the problem from before the current update, where you needed to either disconnect the fan wire or force a workaround, because the thermostat was turning on the fan prematurely through the G wire. But now with the update, as long as you use select the “gas - forced air” option (make sure you delete the thermostat and then set it back up), you should have the By Furnace option on the Advanced screen and Fan Activation Delay. By using the By Furnace setting, your furnace controls the fan, which is what you want, rather than the thermostat controlling the fan. You should be good to go.
My assumption is gas and forced air combination gets you the “by furnace” option. Whereas LP and forced air or Oil and forced air does not. I tried the LP and no option. Switched it to Gas and now it’s there. I am assuming heating oil option is the same issue
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I have a furnace that works off of electricity, and I had to set it up with the “gas - forced air” selection so I would get the furnace’s built-in fan time-delay; otherwise cold air would come out when the furnace first turned on.
My guess is that Wyze, through an “abundance of caution” philosophy (as well as their lawyers), decided to force the fan on whenever there is a call for heat, so there would be no chance of Wyze’s equipment being responsible for damage to the furnace, a fire (or leaking CO in case of a gas installation). So they limit the use of the fan option to only forced air - gas. I guess that is the safe choice that will keep Wyze out of trouble. Bottom line is this: If you know for a fact that the furnace is working properly and is controlling the fan correctly, then it is safe to install the thermostat with the “gas - forced air” setting (regardless of what you really have), and then make sure the Fan Delay setting is set to “By Furnace”.
You can easily tell if it’s working properly by just testing it: with NO WIRES HOOKED UP to the thermostat, just short out the W (or W1) wire to the R (or RH) wire. You should hear the furnace cycle on immediately and then the fan will either turn on immediately or will turn on, usually in less than a minute. If it does, then all’s good and set up the Wyze thermostat with the “By Furnace” option. I would suspect that 90% of the time the fan will turn on immediately or within a minute of the furnace heating up (unless the furnace is in some sort of pause or delay mode).
In the rare instance that the fan doesn’t turn on after a minute or two, then short the fan’s “G” wire to the W & R wires. The fan should now turn on. If the fan still doesn’t turn on, then either your G wire is broken or something is wrong with the furnace’s fan or control logic. Easy to check which it is by going over to the furnace, and do the test directly on the terminals.
If the fan turns on only when the G wire is shorted, then you DO NOT want to use the “By Furnace” option since the fan will never turn on and this could lead to trouble (see above 
). Either set up the thermostat as anything but the “gas - forced air” selection (and you’ll get no fan-delay option), or you can set it up with the “gas - forced air” and use the 0, 15, 30, 45 or 60 second delay, but you’ll have to be super careful when setting it up this way because you don’t want to overheat the furnace or cause a safety issue.
The good news is that if you know what you’re doing, you now have some choices on how to set it up. If your old thermostat worked, then you should be able to setup this thermostat so it also works properly (except for the dreaded C wire issue, which has its own issues and thread 
).
So I deleted the T-Stat and re-setup saying it was gas forded air instead of oil forced air and I now have the fan delay options in advance settings. I selected furnace control which I assume means it doesn’t send a fan signal at all when calling for heat and leaves it up to the furnace (as it should be).
I’m not sure why the option doesn’t show up under oil forced air, but does on gas, but oh well. Normal thermostats don’t care about the fuel.
Interesting that it’s been since early release that I did setup and Wyze still hasn’t fixed the wiring setup bugs after all this time. Just like in the past, I told setup I only had C, Rh, W, and G wires and heat only, but still got the error about several missing wires after that like Y1, etc.
Sorry for the very late response, but I just saw this. My Thermostat has a “Fan activation” delay option of “by furnace” but it will not allow me to select it. It reverts to 15s? Why is this?
I noticed that on mine as well now. It had been working as “let the furnace decide” before I deleted and re-added to try and get two stage two heat and A/C to work. I actually use propane and I think I remember I had to select natural gas to get it to allow me to use the “let the furnace decide option”. May have to delete and recreate again to see for sure.
Thanks for your comments, let me know if you delete and recreate again.
Mine is working now - I can select “let the furnace decide”
After I saw your post I went in and checked. Still could not select by furnace. Then I realized there was a Wyze app update for my iPhone. Did that, went back in and am now able to set he control back to furnace. Glad they fixed it. Until something else breaks due to [Mod Edit] QC.
MOD NOTE: Post edited to conform to the Community Guidelines.
I can select “let the furnace decide” but when I click Save it reverts back to 15s
Is anyone else still having issues with this?
I’m in North Florida and we’re starting to get a cold snap, and it seems like the fan is constantly running and my house isn’t heating at all.
Have set the thermostat to Auto and home model, and it just stays at 63 with the fan symbol running for what has been the past half hour.
I’m running firmware version 1.2.7, not sure what information I need to pass along, but can anyone help me out?
Do you have a heat pump? if so, what is the backup source of heat, and how is it wired?
Pictures of the thermostat wiring, old thermostat wiring and furnace wiring are very helpful for troubleshooting.