Troubleshooting and Support

If you have difficulty with your thermostat, please try the following suggestions. Most problems can be corrected quickly and easily.

Display is blank:

  • Check circuit breaker and reset if necessary.

  • Make sure power switch for heating & cooling system is on.

  • Make sure furnace door is closed securely.

  • Make sure the C wire is connected.

Heating or cooling system does not respond:

  • Press Menu > System Mode > Heat > Done to set the system to Heat mode. Make sure the desired temperature is higher than the indoor temperature.

  • Press Menu > System Mode > Cool > Done to set the system to Cool mode. Make sure the desired temperature is lower than the indoor temperature.

  • Check circuit breaker and reset if necessary.

  • Make sure power switch for heating & cooling system is on.

  • Make sure furnace door is closed securely.

  • Wait 5 minutes for the system to respond.

Temperature settings do not change:

Verify the thermostat is set to the correct mode. Press Menu-Mode to change mode setting.

If the display indicates “screen locked” when you press the up or down arrow, you can unlock the screen by selecting menu-security settings.

The thermostat may be preventing you from changing the set-point above or below a certain setting because of installer configured minimum and maximum settings. See the ISU settings for 4100.

Default minimum and maximum settings:

  • Heat: 40 °F to 90 °F (4.5 °C to 32.0 °C)

  • Cool: 50 °F to 99 °F (10.0 °C to 37.0 °C)

Heat runs with thermostat in cool or off mode:

Does the display show “Freeze Protection active”? If so, the installer set the thermostat for a freeze protection temperature that maintains a minimum temperature even when the thermostat is set to off or cool. This feature will generate an alert message if the temperature drops below the freeze protection setting.

Aux heat runs in cooling:

  • For heat pump systems, verify there is not a wire attached to W on the UWP.

Cool runs with a call for heat:

  • Verify that the O/B wire is making a good connection and verify the changeover valve setting is correct for the heat pump used (ISU 2060).

Heat doesn’t come on:

Verify the thermostat is set to Heat, Em Heat, or Auto mode and verify that the heat setpoint is above room temperature. Does the display indicate “Heating to” with an orange display screen? If so, the thermostat is attempting to run the heat.

  • If “Heating to” is displayed in orange, and heat does not come on after a short delay, verify the wire connections, R/Rc slider jumper on UWP (or R, Rh, and Rc jumpers if an EIM is used). If those variables check out, your HVAC contractor can call Tech Support to verify configuration and for further troubleshooting.

  • If display isn’t showing “HEATING TO” (rather than “HEAT TO”) or “WAITING FOR EQUIPMENT” but heat setpoint is above room temperature, go to EQUIPMENT STATUS.

  • See if there are any active alerts. The T10+ with EIM can be set to lock out the heat during an active alert. A custom Dry Contact Alert set to lock out heat could have been snoozed (or set to not display alert message by installer) but equipment status would show the heat as “Idle (Dry contact lockout)”. If display shows “waiting for equipment” then the thermostat is holding off running the heating to prevent short cycling. This delay should last 5 minutes at most. If you time this and it is longer than 5 minutes, it is possible you are intermittently losing power to the thermostat. As a test you could remove all wires besides R and C from UWP (or EIM if T10+ is linked to an EIM and then test the heat. If the thermostat then indicates a call for heat within 5 minutes, a shorted wire or high equipment draw could be interrupting power to the thermostat momentarily at the start of a heat call.

Cool doesn’t come on:

Verify the thermostat is set to Cool or Auto mode and verify that the cool setpoint is below room temperature. Does the display indicate “Cooling to” with a blue display screen? If so the thermostat is attempting to run the cooling.

  • If “COOLING TO” (rather than “COOL TO”) is in a blue display, and cooling does not come on after a short delay, verify the wire connections, R/Rc slider jumper on UWP (or R, Rh, and Rc jumpers if an EIM is used with T10+). If that all checks out contact HVAC contractor. Contractor can call tech support to verify configuration and further troubleshooting.

  • If display isn’t showing “COOLING TO” or “WAITING FOR EQUIPMENT” but COOL setpoint is below the room temperature, go to EQUIPMENT STATUS.

Check for any active alerts. The T10+ with EIM can be set to lock out cooling during active alerts. A custom Dry Contact Alert set to lock out cooling could have been snoozed (or set to not display alert message by installer) but equipment status would show the cooling as “Idle (Dry contact lockout)”. If display shows “waiting for equipment” then the thermostat is holding off running the cooling or to prevent short cycling. This delay should last 5 minutes at most. If you time this and it is longer than 5 minutes, you may be intermittently losing power to the thermostat. To test, remove all wires besides R and C from UWP (or EIM if T10+ is linked to an EIM) and then test the cooling. If the thermostat then indicates a call for cool within 5 minutes, a shorted wire or high equipment draw could be interrupting power to the thermostat momentarily at the start of a cool call.

Weather menu isn’t displayed:

This menu is only shown when the thermostat is connected to WiFi and the app. If WiFi connection is lost, the thermostat will not show that option until connection is restored.

Cooling runs below setpoint:

Verify the cooling is running while cool setpoint is above the room temperature reading on the display. If so, verify the thermostat is deliberately running cooling. When doing so, the display is blue and it shows “Cooling to” (rather than “COOL TO”). Also, menu equipment status will show if the thermostat is trying to run cooling or not.

  • If the display shows “Cooling to” and a setting that is above the room temperature reading it is likely the T10 or T10+ has been set to over-cool when humidity is high. Go to the Dehumidity setting in MENU. If that display shows a status of “DEHUMIDIFYING” select OPTIONS and deselect USE DEHUMIDIFICATION. Then go back to the home screen and see if the cool call ends. The T10 or T10+ can run the cooling up to 3 degrees below the cool setpoint if configured to use the air conditioner for dehumidification.

Fan is running unexpectedly:

  • The T10 & T10+ has different settings that might have turned on the fan. Check EQUIPMENT STATUS to see what the T10 or T10+ indicates it is running.

  • The T10 & T10+ could be set to run the fan with a call for ventilation, humidification, or dehumidification.

  • The T10 or T10+ will also run the fan with a call for cooling and in forced air systems the fan will also run with a call for heat (but this may or may not be controlled by the thermostat depending on the system type settings).

  • There are ISU settings for extended fan run in heat or cool mode (ISU 3260) which can be set for up to 15 minutes.

  • Additionally, the T10+ has a “TEMPERATURE AVERAGING” option to run the fan to average hot spots and cool spots if a remote sensor is used. This would have been configured by the installer in the ISU. To see if this is being used, go to menu and look for TEMPERATURE AVERAGING. If that option appears, select it and see if it is currently active.

  • The T10 & T10+ can have the fan set to on, auto, or circ for each schedule period.

  • If the thermostat doesn’t indicate the fan is on under the EQUIPMENT STATUS menu, it is possible something else in the system is controlling the fan such as a separate control for a humidifier, dehumidifier or ventilator.

Fan will not run when expected:

If the thermostat is set to control a heat-only system such as a boiler, there will not be a fan setting. Check equipment status. This will show the fan state. If it says “Idle (Fan Lockout)”, then the installer configured the T10+ to lock out fan at the end of a call for cooling for anywhere from 5 to 90 minutes (ISU 3125). This is set up for some homes in very humid regions where running the fan at the end of a cool call can blow air over a wet coil and re-introduce humid air back into the space.

Display doesn’t show indoor humidity:

The T10+ has an ISU setting to not display indoor humidity (ISU 14050).

Display changes color or goes blank at night:

There are multiple settings under Temperature > Display > Inactive Night Backlight (on T10+) or Inactive Sleep Backlight (on T10). These settings allow you to set a time for the display to go dim or go dark. (Dark option on T10+ only).

I cannot link my T10+ to the EIM:

Verify that you have a T10+ rather than a T10 and that you have the correct EIM for this model. T10+ models are THX321WF3003W and THX321WFS3001W

  • EIM is THM04R3000

  • The T10+ and EIM are included in YTHM1004R3000 and YTHM1004R3001 kits.

  • If the T10+ had already been configured without an EIM, you need to do a factory reset of the thermostat to get to the initial screen that allows you to choose to use it with an EIM. Then follow the instructions on T10+ display.

I cannot link my T10+ to the wireless outdoor sensor:

Verify that you have a T10+ rather than a T10 and that you have the correct wireless outdoor sensor for this model. T10+ models are THX321WF3003W and THX321WFS3001W

  • Outdoor sensor is C7089R3013 (not C7089R1013)

  • The T10+ and outdoor sensor are included with an EIM in the YTHM1004R3001 kit.

  • See the instructions for adding an outdoor sensor in this document.

Wi-Fi and app-related issues:

See WiFi Setup.

Active Rooms is selected but one or more of my sensors doesn't register activity:

Go to MENU/PRIORITY ON THERMOSTAT. Verify active rooms is selected. View the status of the sensor(s) in question in that screen. If there is not an indication of occupancy by that sensor (green person next to sensor name) move in front of the sensor. If that doesn't change the status of the sensor:

  • Verify the sensor you are testing is the one you see in the display. To do so, go to Devices and Sensors and select the sensor name.

  • Verify the Use Motion slider is set to Enabled.

If so, select OPTIONS/BLINK LIGHTS. Go back to the sensor and verify it has a blinking light.

If not, check the other sensors in the home to see if the sensors were placed in the wrong rooms.

C7189R2002 or C7189R3002 wireless indoor sensor will not connect to my T10 or T10+:

Following the discontinuation of C7189R2002 sensors and the introduction of C7189R3002 sensors, there was a period during which the new sensors worked with existing T10+ thermostats and the new T10+ thermostats worked with the existing sensors.

Beginning with units manufactured in Autumn 2024 (date codes 2440 and later) T10+ thermostats will only work with C7189R3002 sensors and C7189R3002 sensors will only work with T10+ thermostats. Older thermostats and sensors that cannot connect should be replaced.

Thermostat is losing time:

If the T10/T10+ is used with HomeKit without registering the thermostat to the First Alert or Resideo app, it may lose time. We recommend registering the thermostat to the First Alert or Resideo app, even when controlling it through HomeKit.

Customer Assistance

For assistance with this product, please visit customer.resideo.com.

Or, call Resideo Customer Care toll-free at 1-800-633-3991.

5-year limited warranty

For Warranty information go to honeywellhome.com/support