Wyze thermostat fan control issues started today

My thermostat has worked fine for the last 9 months or so but today I noticed my house temp rising. I just did a little investigating and here is what I found:

Compressor was running and evap was frozen beautifully
Switching fan to manual had no effect
Raising cool to temp resulted in compressor being turned off
Powered down the air handler and found no wiring/board issues of note.
Reapplied power and fan started ~ 5s after power was applied despite not being in cool mode
Turned fan to “on” and fan continued to run
Turned to auto and continued to run.
*Rinsed and repeated three times with no change after power cycles
Changed to spare dumb thermostat, unit performed as expected through 5 auto/on fan cycles and 1 cool cycle
Replaced Wyze thermostat, fan issue resumed.

Before I send this thing back to the mother ship for repair, has anyone else seen an issue like this? Any chance you found a solution?

Send some pics of your wiring, others could notice something potentially.

Evap Freeze-up is usually caused by a lack of warm return airflow to the air handler resulting in insufficient cooling of the warm air. There is no heat transfer from the air to the coil to keep it from freezing. This is usually caused by plugged filters or something blocking the warm air return. It can also be caused by blocking\closing too many outlet registers or by a blocked condensate drain causing excess moisture. Lastly, if the setpoint is too low on an excessively hot and humid day, the unit can freeze up just from being overworked and overtaxed.

The usual remedy for this is to change filters and open all vents so that the coil can fully thaw. If there is airflow coming out of the registers, running the fan only with the AC off will speed up this thawing. Also verify that your evap condensate pan drain or condensate pump isn’t blocked and not allowing the condensate to exit the pan. A full evap and pan clean out is in order.

As for the T-stat, my Wyze T-stat installed with different fan run times than my old dumb thermostat. I had to adjust those in the advanced settings. It is possible that the Wyze T-stat is following whatever programming is already in those settings.

If I couldn’t get mine to work after the steps you took, I would first shut everything off and look at all the settings. Because of the differences in fan operation because of the coast to cool function and minimum runtime settings, I would make sure those are all off. Then I would run the system test within the app. If this didn’t work, I would then opt for a reinstallation of the T-stat from scratch.