Honeywell Thermostat Not Working: Troubleshoot Guide

Troubleshooting Procedure

I’ve broken this guide into two sections for easier explanation:

• Scenario 1: If your thermostat has a blank display and is not responding to any button presses, then continue reading.

• Scenario 2: If your thermostat has an active display that responds to touch, but, the heating or AC unit is not turning on or reaching the set temperature then jump to Scenario 2. In this case, the thermostat may possibly flash an error code or message like “cool on”, “heat on”, “wait”, “waiting for equipment”, or specific thermostat error codes. This could indicate an issue with the cooling system, requiring you to check the thermostat settings, wiring, power source, and overall equipment functionality. Additionally, performing a thermostat reset might be a necessary step in the troubleshooting process.

Scenario 1: Troubleshooting a Blank Screen on the Thermostat

If the thermostat display is not waking up to button presses or touch gestures for smart thermostats, it may be a malfunction, an electrical problem, a blank screen, or the device may be out of power.

Besides that, it can also indicate an issue within the internals of the thermostat. A malfunctioning furnace door switch can prevent the thermostat from working properly.

So let’s walk through the troubleshooting steps in a blank display, step by step.

So let’s walk through troubleshooting a blank display, step by step.

Step 1. Check if the Thermostat Panel is Pressed In

First, you want to check if the thermostat panel is firmly pressed in.

If it’s not, make sure to take it out, unscrew any fasteners, and re-install the panel. The new thermostat panel should stay flush with the wall plate.

Even if the panel isn’t loose, I highly recommend to gently pull the thermostat panel and reinstall it for good measure. While you’re doing so, make sure to follow the second step.

Step 2. Check the Thermostat Wiring

So while you’re unplugging the thermostat panel, it’s a good idea to check the thermostat wiring for loose connections or damage and verify the thermostat settings are correct.

The wiring configuration may vary based on your system setup, but always check for the red-colored R-wire and make sure it’s connected securely to the appropriate terminal.

Beyond that, you can check for the black-colored C wire, if your thermostat doesn’t run on batteries. Additionally, ensure the G terminal is properly connected, as it activates the fan to circulate cooler air in your home.To learn more about thermostat wiring, you can check out this guide.

Step 3. Check the Batteries

After checking the wiring, it’s also a good idea to check the thermostat batteries, and possibly replace them if you haven’t done so in a while.

Even in cases of screen flickering, fading, or completely turning off, replacing the batteries might quickly solve your issue.

Most thermostats have batteries and still take power from the HVAC system, but some models work only on batteries. Nevertheless, replacing the batteries is always a good idea.

Also, don’t forget to check out my extensive guide on how to replace batteries for all Honeywell thermostat models.

Now, reinstall everything and see if the thermostat lights up.

Step 4. Check the Power

If the panel doesn’t power on, even after following through with the steps above, it could be due to an electrical problem. Check the circuit breaker and the lights on your HVAC system, and ensure the thermostat power source is functioning correctly.

Also, look for any safety switches near the unit. If your thermostat has one, make sure it’s flipped to the “on” position.

Step 5. Check Furnace Doors

If your thermostat is connected to a furnace, it is possible that the furnace door is not shut properly. Furnaces usually have a door switch, and some thermostats are extremely sensitive to the furnace door switch as it’s a safety concern. A malfunctioning furnace door switch can prevent the thermostat from working properly.

Check if doors are closed and sensors and indicators are working. If the door switch is broken or seems to have damaged wires, you might need to get it replaced with the help of a technician.

Step 6. Check the Voltage in the Thermostat Wires

If you’re comfortable tackling electrical components yourself, and you already have a multimeter on hand, you can check the thermostat voltage by measuring the DC voltage coming in from the HVAC system and connecting to the thermostat.

Remove the thermostat panel from the mounting plate and check the DC voltage between the R and C contacts. For most systems, they need to be around 24-30V.

If you find a lower voltage, it might mean a wiring error or fault within the HVAC system, or an electrical problem.

Optional Step: Try Bypassing the Thermostat

If you have access to a tool or a contraption to create a jumper wire, you can try a thermostat bypass.

This isn’t a proper solution per se, but with this method, you can confirm if the issue lies within the thermostat and not the HVAC.

To bypass the thermostat:

• Turn off the breakers for the thermostat and the rest of the HVAC (furnaces, heat pumps, etc.)
• After that, remove the thermostat panel from its wall mount
• Fix one end of the jumper to the R contact and the other end to the AC or furnace contacts. Usually, it’s Y for cooling and W for heating.
• After the jumpers are installed, switch the power back on and see if the HVAC kicks in.

If the furnace or AC unit powers on without any issues, you can safely rule out the HVAC system. Then, the issue is definitely within the thermostat itself.

Conversely, if the HVAC doesn’t work, you might have to troubleshoot it further.

Scenario 2: Troubleshooting the HVAC not reaching the set temperature

In this scenario, your thermostat has an active display that responds to touch, however, the heating or air conditioning system is not reaching its set temperature. In this case, the thermostat may possibly flash an error code or message like “cool on”, “heat on”, “wait”, “waiting for equipment”, or specific thermostat error codes. To troubleshoot, check the thermostat settings and ensure the power source is functioning correctly.

If a specific error code is showing, I recommend checking out this error code guide here.

Step 1. Change the Temperature

The first thing you can do if your thermostat display is on, but doesn’t power on the HVAC, is to adjust the thermostat temperature settings.

So, first, try changing the temperature on your Honeywell thermostat.

Also, make sure the desired temperature falls within the acceptable ranges.

Specifically, set the heating between 40 °F to 90 °F (4.5 °C to 32.0 °C) and the cooling between 50 °F to 99 °F (10.0 °C to 37.0 °C). If you go beyond these ranges, the HVAC won’t kick in.

Step 2. Wait 5-10 Minutes

If your display shows a “wait” message, or flashes “cool on” or “heat on,” you can simply wait it out for five minutes or so, which is known as the thermostat wait time.

This step helps you safely rule out the compressor protection feature.

Step 3. Change the Temperature Mode

However, if the HVAC doesn’t power on after that, try resetting or changing the thermostat mode first. This can help the thermostat reconfigure itself.

Also, if you find that the heating unit works while the cooling does not (or vice-versa) you can easily tell that the issue lies within the component that doesn’t power on.

Step 4. Verify the Temperature Sensor is Working Correctly

In certain situations, although rare, the thermostat sensor inside the thermostat, or the one connected to it, might be malfunctioning. In this case, it’s a good idea to verify the temperature readings using an external temperature gauge to ensure accurate temperature readings.

If the room temperature displayed on your thermostat or smart sensor isn’t consistent with the reading on a thermometer, it might imply the sensor is faulty.

Faulty Smart Sensor

In the case of faulty smart sensors (like the T9 smart room sensor), you can unlink the smart thermostat sensor from the app and replace it with a new one later (or replace the battery in the sensor).

Fault in the Embedded Temperature Sensor in the Thermostat

If it’s the temp sensor in your thermostat that’s incorrect, you might have to get the embedded thermostat sensor looked at by a technician or replace it entirely.

Step 5. Check the Wiring

Weak splices, wrong or loose connections, exposed wiring, or a faulty thermostat may cause issues and prevent your thermostat from working properly.

In this case, isolate the circuit, unscrew the thermostat, and check if the wires are connected correctly to address any thermostat wiring issues, and verify the thermostat settings are accurate.

Check if Y and Y2 are attached to the correct color wire for cooling. For heating, check if W and W2 are attached to the correct color wire.

Also, you may want to verify if there are Rh and Rc wires in your system and whether they are attached to the proper terminals identified by the correct color.

Step 6. Check Individual Components

If possible, you can check all the individual thermostat components of your HVAC, including the air conditioner, air filters.

This might include checking the switches, indicators, fuses, and wiring for your furnace, heat pump, and AC unit, and ensure the power source is functioning correctly, and verify the thermostat settings are accurate.

Final Step: Call in the Experts

When all else fails and your Honeywell thermostat remains unresponsive, consider seeking professional help from a thermostat technician.

A technician can quickly identify and fix common issues, such as damaged wiring, malfunctioning capacitors, obstructed sensors, or blown fuses, while also inspecting components like the compressor, condenser, or fan motor.

Conclusion

A Honeywell programmable thermostat will stop working either because the display is off or the HVAC is not responding.

By following the steps outlined for each situation, including checking the thermostat settings and power source, you can get to the root of the problem and ensure it won’t happen again.

However, make sure to call in a professional support if you’re not comfortable diagnosing electrical components and always follow the proper safety precautions.

This article serves as a thermostat troubleshooting guide to help you address common issues with your Honeywell programmable thermostat.

Sources

• https://www.honeywellhome.com/us/en/support/air/thermostats/product-selector/device-not-working/
• https://www.honeywellhome.com/us/en/support/lyric-thermostat-troubleshooting-7/
• https://www.honeywellhome.com/us/en/support/why-is-my-thermostat-wifi-not-working
• https://www.honeywellhome.com/us/en/support/when-setting-up-my-t5-or-t5-plus-t6-pro-wifi-cannot-connect-to-my-wi-fi/