Wyze Thermostat Problems

It took me a long time to figure out why my Wyze Thermostat was not working properly, but I finally fixed it – or so I thought.
Here’s the problem. When my heat comes on, my furnace is using the high-speed fan mode, usually reserved for cooling (since cold air is heavier). Then, 30 seconds after my heat shuts off, it comes back on again, but this time in low-speed fan mode. It runs for about 30 seconds and then shuts off.

My house has a forced-hot-air system, using gas. With my original Honeywell thermostat, there was a Blue C wire that was not being used. I hooked up the Blue wire with the Wyze thermostat (I did not use the Wyze adapter) and the A/C worked fine this summer. But the heat is not working so well.

Can you provide a picture of the Wires on the T-Stat and a Picture of the Wiring on your HVAC control board


Here you go:

What is your fan delay set to?

My fan delay is set to 30 seconds.

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Try setting it to off or “by furnace”

You appear to have an older style furnace that doesn’t expect to have a signal on G when the heat is called.


Thank you. I will try that.

My furnace is original to my house, built in 1987. Still running strong. :wink:

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I hope you don’t mind me sayng this, but you are an absolute genius! I set my fan delay to “By Furnace,” and it works perfectly. I wouldn’t have thought of that in a million years. Thank you so much!


Well, I thought my furnace was working properly. The heat comes on and shuts off when the selected temperature is reached. But a couple of minutes later, the furnace turns on again, and runs for only 15 seconds.
Curious why it is doing this!

Do you have Coast to Cool enabled?

I can understand a brief pause, but not a couple minutes.

No, I don’t have Coast to Cool enabled. And it’s more than a brief pause.

Apparently my furnace is “short-cycling.”


You said that your furnace runs normal on a call for heat and brings it up to temp, shuts it down at temp, but then restarts minutes later and runs for 15 seconds even though it is at temp.

Short cycling is usually a heat pump problem, not a gas furnace problem unless you have an overheat sensor doing an emergency shutdown because of restricted airflow in the air handler. And since you have already programmed the thermostat to allow the furnace board to determine the fan cycle and delay run time we can rule that out.

How do your air supply filters look?

My filters are clean; I replace them regularly.

Some observations: This morning, my heat came on, reached the temperature set on the thermostat, then shut off. One minute and 50 seconds later, the furnace came on again and ran for 15 seconds before shutting off.


Can anybody help with this?

Sorry, if setting it to by furnace didn’t fix it, I’ve got no idea. that should disable thermostat control of the fan during heating mode. You could disconnect the G wire for now, but you’ll want to reconnect it before you turn on the air conditioner.

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Thanks. Usually the pilot light (flame) is on, and when I set the thermostat higher, the burner kicks in and I see a lot of flames in the furnace. When the temperature is reached , the furnace shuts off and goes back to pilot light only.
But then, about 2 minutes later, the furnace blower comes back on for 15 seconds, then shuts off. During this time, the flames don’t re-ignite, just the pilot light stays on. Very strange.
What will happen if I disconnect the G wire? Will my furnace still work?

G controls the main blower fan, and nothing else. If your wyze is set to “by furnace”, it already shouldn’t be sending a signal on G, the furnace is supposed to control that itself.

If you disconnect G, you won’t be able to turn the fan on and off with the thermostat, but the heat should work fine, and the blower should still be controlled by the furnace itself.

It’s important that you reconnect it before turning on the air conditioning, because unlike the furnace, the air conditioner won’t generally have a way to run the blower fan by itself - it relies on the thermostat to do that.

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Thank you very much for your help. I will try disconnecting my G wire. Hopefully that will temporarily fix things. I will write myself a note to reconnect it in the summer! :wink:

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