I read where someone else having this issue and they went back through the set up and changed one of the settings. Originally they chose gas heat and then forced air but they said they changed the forced air setting to the other option and that stopped it from happening. Sorry its kinda vague but might be worth checking out
I just found this thread about the same issue and it seems like they are saying it’s the G wire like you mentioned. Maybe someone else will have more input, or ran into this and fixed it another way. Mine is all electric heat pump so I didn’t have the issue.
Re-did the setup and chose gas fuel and then other under type, not forced air.
Tested and ran like it should (waited to heat up before the fan comes on, furnace controlling the fan not the thermostat).
But I lost the ability to control the fan manually.
The option is still there in the app to turn it on but it doesn’t do anything.
I guess I’ll leave it like this for now until summertime.
I had the same problem. When I turned on my thermostat the blower would kick in immediately, blowing cold air for a minute. Very annoying. Also, it was using the high speed mode of my blower, which is usually reserved for A/C.
The solution? I simply disconnected the G wire in my thermostat, and the problem is solved. Now the furnace heats up the heat exchanger before the blower turns on (in low-speed mode). Note: I am using a setup with the C wire and no C adapter.
EDIT: Sorry, didn’t see the posts where removing the G wire was discussed. I didn’t know this would remove manual control of the fan.
I was experiencing the same issue with Main Blower Fan immediately turning on during the heating cycle.
I found that my Furnace control board has (G) and (GH) terminals. (G) terminals control the main blower fan, not the smaller draft inducer fan. I searched my furnace model found that the (GH) terminal is for heat only systems. Which is what I have.
After connecting to (GH) and testing, the furnace is now operating the same as the old thermostat.
The burner lights first and once the heat exchanger comes to temp the main blower then turns on. Once temp is reached the burner shuts off and the main blower runs until the the heat exchanger cools.
I am no longer getting the immediate blast of cold air when the thermostat triggers a heating cycle.