Fan runs constantly - wiring issue?

The thermostat seems to be heating and cooling successfully but the fan is running constantly. I don’t think it’s a setting (fan is set to auto not on, and is set to 0 min per hour), so maybe a wiring issue?

Here is the original thermostat wiring:

Here is the wiring on the unit (it’s an AC and Heat Pump unit):

And here is how the app suggested to wire the thermostat, just swapping W2 to W1:

If you disconnect the green wire from G, does the fan stop? note: this is a troubleshooting step, not a permanent fix suggestion. Reconnect it after testing.

Also, what’s this?


With the G wire disconnected the fan doesn’t run.

I sent my husband in the crawspace for the initial unit picture, he noticed it but assumed it may have been a ground wire. We had some HVAC work done, does that look like something they may have missed reconnecting?

If taking the G wire off makes the fan not run, then it’s not a wiring issue, rather the thermostat is telling the fan to run. You could have a defective thermostat, or you might have one of the settings in advanced setup set improperly. With the thermostat in the “off” mode does the fan run?

1 Like

Yes, with the thermostat control off and the fan on auto (options are only auto or on) - the fan is still running. I have to flip the breaker to get the fan off.

I really appreciate the help troubleshooting.

I checked the advanced settings and nothing is jumping out to me as causing the issue, anything I should look out for?

1 Like

It sounds like a defective thermostat. Either there’s a solder bridge on the board allowing current to bypass the relay, or the relay for the fan is stuck on. Contact wyze support and ask for a RMA.

1 Like

I am having the same issue. I have another Wyze thermostat that is connected to a different AC unit and fan control works fine there. So moved it to this unit for testing and fan turns on as soon as it is connected. Same thermostat behaves differently on different unit without reprogramming.
The original Honeywell thermostat does not do this. Checked the voltages (had only power connected for this testing) - Wyze - when fan is off, the G wire voltage sits at 3.6V, when fan is on it goes to the Rc voltage. Checked on the Honeywell and when fan is off, the voltage goes to almost 0V.
I think this is a Wyze issue, Wyze needs to short G to ground to turn fan off? Looks like it depends on the AC system.

G should be pulled up from 0 to 24v when fan is called- if it’s floating at 3.6v when not being called, there’s something wrong,

That is a similar situation to mine. The G had low voltage even when not being called for, causing the fan to run constantly. This was for a brand new HVAC Heat Pump system, so after we did our own troubleshooting for a few days we had the installers back out who confirmed it was the thermostat and we let them install the Honeywell they had.

The fact that your thermostats behave differently on different HVACs, maybe I didn’t have a bad thermostat. Although my wiring setup should have worked, perhaps it was just a compatibility issue.

Having the same issue here (new Trane HVAC system installed). Are you just running the Honeywell? Or did you figure something out with the Wyze?

Also bought a brand new Wyze thermostat to test to see if there was an issue with the one I had or even something off with the back plate. Ended up with the same issue.

Honeywell installed by the HVAC company works as intended.

Trane - Heat Pump - Heat Strips - New thermostat wiring - Photos match almost exactly as above except the Wyze had me plug into the * instead of the W1 (I’ve tried both options though)

cc: @vk1 @speadie