Picture of the Honeywell wireless thermostat, displaying its -Lost Wi-Fi Signal- message.

How to Fix Honeywell WiFi Thermostat Connection Failure

We show here how to fix Honeywell WiFi thermostat connection failure issues, as seen on man Honeywell internet controlled thermostats from time to time.

How to Fix Honeywell WiFi Thermostat Connection Failure

Picture of the Honeywell RTH9580WF smart thermostat, displaying the -Connection Unsuccessful- screen, due to an incorrect network password.
Honeywell RTH9580WF smart thermostat, displaying the -Connection Unsuccessful- screen, due to an incorrect network password.

By this, we mean that the thermostat was connected properly prior to the failure, but has recently lost its wireless connection, and will not reconnect to your home Wi-Fi network. Typical causes for this sort of connection failure are listed below.

1.1 Wi-Fi Network Not Found in Scan

Problem

Your wireless network does not show up in the list of in-range networks that the Wi-Fi thermostat discovers during a Wi-Fi scan when you try to reestablish the network connection.

Solution 1.1.1

Make sure your wireless router is powered up and that your WiFi SSID is not hidden (being broadcast).  Most routers and access points broadcast the network name SSID by default.  However, you may have intentionally hid your SSID for security purposes.  If so, then your SSID will not appear in the in-range networks list when the thermostat scans for available networks.  So you must enter your network name manually as well as the security protocols it uses (WPA, WEP, WPAT, TKP, AES, …).  Most thermostats feature an Other button to press, to cover the case where your network does not appear in the list.  When you press that, you’ll be prompted to enter your network details as discussed.  Be careful to avoid typos however.  An incorrect network name, password, authentication, or encryption protocol entered here will prevent your thermostat from connecting.

Picture of the Honeywell RTH9580WF thermostat, displaying the Select WiFi Network screen, with the Other... option highlighted. How to Fix Honeywell WiFi Thermostat Connection Failure.
Honeywell RTH9580WF thermostat, displaying the Select WiFi Network screen, with the Other… option highlighted.

1.2 Wi-Fi Network Parameters have Changed on your Router

Problem

That is, the access point password, network name, or network security settings may have changed, but have not yet been programmed into the thermostat.  This often happens when you buy a new router, one that has a different default wireless network name and password.

Solution 1.2.1

Determine your correct Wi-Fi network name and password, and then run Honeywell thermostat WiFi setup again.  There, set up the thermostat to connect to that wireless network.  Some thermostats require a hard reset to change the wireless network that they try to connect to upon start up, such as the RTH8580WF does.  But others, such as the RTH9580WF pictured next, allow you to go in and modify the network settings without a factory default reset.

Picture of a Honeywell Wi-Fi touchscreen thermostat, with the Wi-Fi setup option highlighted.
Honeywell Wi-Fi touchscreen thermostat, with the Wi-Fi setup option highlighted. 

1.3 How to Fix Honeywell WiFi Thermostat Connection Failure: Router Requires a Reboot

Problem

Your wireless router may have received an update, been subjected to a power surge, or experienced the manifestation of a firmware bug.  These gotchas may corrupt the RAM in the router, and interfere with how it responds to connection requests from Wi-Fi based appliances, like the Honeywell wireless thermostat, and triggered the thermostat connection failure.

Solution 1.3.1

Restarting the router clears out its main memory, allowing it to start afresh from a known-clean point.  Rebooting a router / access point often restores proper router operation, and can resolve many new connection failures without taking further troubleshooting steps.

1.4 Interference Preventing or Interrupting Wireless Connection

Problem

Perhaps you’ve bought a new appliance, wireless phone, Bluetooth speaker, or other network enabled device that is now interfering with the wireless connection.  Most Honeywell WiFi thermostats communicate using the 802.11g Wi-Fi standard.  These transmissions occur in the 2.4 Ghz. frequency range.  Now 2.4 Ghz. is also a popular frequency band for many devices, including other Wi-Fi networks as well as non Wi-Fi devices such as cordless telephones, microwave ovens, baby monitors,, and RF-based remote controls.  There’s a lot of traffic in that frequency range therefore, particularly in crowded row homes or otherwise closely spaced housing.  So occasionally, you may experience these thermostat connection failures due to interference from nearby devices like these.

Solution 1.4.1

Eliminate the interference source.

Solution 1.4.2

Try turning off any wireless telephones around your thermostat, and see if the network connection can be reestablished.  If so, replace your phones (including the base unit) with one that operates on different frequencies than 2.4 Ghz.  Many of the newer cordless bases and handsets operate in the 1.9 Ghz. band.  These are specifically designed not to interfere with WiFi communications.  But don’t buy one if you’re not sure what frequencies it operates on.  Otherwise, you could end up with another that still operates on the same frequencies, and your connection failure issues will continue.

Solution 1.4.3

Do similarly with other wireless devices too.  Try turning them all off and see if the connection failure goes away.  If it does, turn each device on again, in succession, and observe what happens on the thermostat after each.  If the thermostat again came back online, but then goes bonkers after you power up a particular device, then that’s likely the one causing the connection failure.  Try moving this appliance further away from the thermostat and router.

Solution 1.4.4

If moving the appliance is not possible, then try repositioning your router closer to the thermostat.  The resulting stronger WiFi signal may then be able to overcome the interference, and restore a reliable network connection to the thermostat.

1.5 Thermostat Too Far Away from your WiFi Router

Problem

Even though the signal strength of the Wi-Fi network to which you’re trying to connect might show as full strength, successful connection still may be prevented by multipath signals between your router and thermostat and / or interference from nearby electronic devices.

Solution 1.5.1

Relocate the router closer to the thermostat.

Solution 1.5.2

Relocate the router farther away from the thermostat.  Occasionally, your network signal may be too strong for the thermostat, overloading its internal WiFi radio.  Moving the router a bit farther away reduces the chances for signal overload.

Solution 1.5.3

Or, try the solutions in problem 1.4 above.

1.6 How to Fix Honeywell WiFi Thermostat Connection Failure: Defective or Misconfigured Router / Access Point

Picture of the Netgear WN802T WAP, unpackaged, shown with its 12-volt power adapter. How to Fix Honeywell WiFi Thermostat Connection Failure.
Netgear WN802T WAP, unpackaged, shown with its 12-volt power adapter.

Problem

Perhaps you, or someone else in your household, inadvertently changed some settings on your router.  Test for this cause by attempting to connect to your wireless router with another Wi-Fi device such as a tablet, mobile phone, laptop, or even a desktop computer via its Wi-Fi connection.  If these clients fail to connect, but did connect before this thermostat outage occurred, then try the following.

Solution 1.6.1

Try resetting your Wi-Fi enabled router to factory defaults, making the necessary adjustments to it for your particular network requirements afterwards, and finally attempting to connect the thermostat again.

Solution 1.6.2

If that measure fails, try a different Wi-Fi router.  Routers, particularly the ones that meet the minimal speed requirements of Honeywell wireless thermostats these days, are quite cheap (under $40), especially if you get them on eBay.  Honeywell wireless thermostats require very little internet bandwidth, and so, generally work very well with even the very cheapest of wireless access points.

1.7 Defective Thermostat

Picture of the Honeywell RTH9580WF Internet Thermostat, being snapped onto wall plate.
Honeywell RTH9580WF Internet Thermostat, being snapped onto wall plate. 

Problem

If none of the above causes turns out to be true, your thermostat may indeed be defective.  While a thermostat failure is rare, nonetheless, over time, most electronic components, including those of the Wi-Fi radio in the thermostat, weaken.  They eventually fail to perform as well as they once did.  The transmission power of the thermostat, due to its aging components, may fall to such a low value that its signal can no longer reach the router.  Wireless thermostat parts are particularly subject to this sort of wear, as the thermostat maintains constant contact with the Honeywell Total Comfort Connect infrastructure on the internet all year round.

Solution 1.7.1

Replace the thermostat.  Try a different Honeywell wireless thermostat.  Like WiFi access point electronics, thermostats do indeed age as well.  If you’re thermostat is more than a few years old, it’s a good idea to replace / upgrade it anyhow.

1.8 Faulty Furnace

Problem

Your furnace supplies 24 volts AC to most wireless thermostats, via an internal power supply, and fed to the thermostat via the wiring that connects furnace to thermostat.  If this supply becomes intermittent, noisy, drops or raises in voltage significantly, the thermostat WiFi connection will likely fail.

Solution 1.8.1

Verify that the AC voltage at the thermostat terminals is 24 volts AC, plus or minus ten percent. If not, call a furnace repair technician, and have her troubleshoot your furnace and repair its power circuitry.

How to Fix Honeywell WiFi Thermostat Connection Failure: The Thermostat Keeps Losing Connection

Consider the following solutions if your Honeywell wireless thermostat is able to connect to your home Wi-Fi network, but frequently loses that connection for the various reasons discussed in this section.

Picture of the Honeywell wireless thermostat, displaying its -Lost Wi-Fi Signal- message.
Honeywell wireless thermostat, displaying its -Lost Wi-Fi Signal- message. 

2.1 Internet Service Temporarily Unavailable

Problem

Some connection failures occur because your internet connection went down.

Solution 2.1.1

Try accessing your internet through another device on the same Wi-Fi network as your thermostat.  If it fails to connect as well, then notify your internet service provider about the problem, and wait for service to return.

2.2 E02 and E43 Error Messages 

Problem

Some Honeywell thermostats display these errors when the Wi-Fi connection fails or cannot be initiated due to the reasons discussed above. 

Solution 2.2.1

Execute items in the first major section above to troubleshoot this network communication failure.

2.3 Router Lost Power: How to Fix Honeywell WiFi Thermostat Connection Failure

Picture of the front of the Netgear N750 WNDR4300 W-iFi Router. How to Fix Honeywell WiFi Thermostat Connection Failure.
Netgear N750 WNDR4300 W-iFi Router, Front View. 

Problem

Perhaps your wireless router has been disconnected from mains power.

Solution 2.3.1

Verify that the router has power and is up and running, by executing items 1. above.

2.4 Modem Lost Power

Problem

In some installations, the cable / DSL modem and router access point are not in the same box, and results in these connection failures.  Yet all of these components must be powered up and functioning properly in order for your thermostat to establish a successful internet connection with the Honeywell infrastructure servers.

Solution 2.4.1

Check the status lamps on the modem, router, and wireless access point to verify operation.  Any red or blinking lights could indicate a problem.

Solution 2.4.2

Check that you can connect to your network with other wireless devices, as described in items 2.1 above.  If not, see the solutions there.

2.5 Honeywell Total Comfort Connect Servers may be Down

Picture of the Honeywell Total Connect Comfort web site, displaying its login page, with active account info filled in.
Honeywell Total Connect Comfort web site, displaying its login page, with active account info filled in. 

Problem

Sometimes, the Honeywell Total Connect Comfort servers are taken offline for maintenance or upgrades.  Or, your own internet connection may have gone down due to storms in the area, downed wires, exterior equipment failures, and so on.  While your thermostat may successfully connect to your Wi-Fi access point, it still may show an error message similar to that in the orange area in the next picture.

 Solution 2.5.1

Wait a few hours for the Honeywell servers to be brought back online.

2.6 Wi-Fi Channel Too Busy

Problem

Most routers generally broadcast on wireless network channels 1, 6, or 11.  It may be that the channel your network is using is highly congested by neighbors’ networks.  Them using their wireless connection may therefore result in a connection failure on yours.

Solution 2.6.1

Change your router’s Wi-Fi channel.  You’ll have to enter the router’s admin pages to accomplish this.  Also, the router will likely reboot after you apply the change.  Try channels 1, 6, or 11, and see if the lost internet connection problem persists.  If you have access to an Android tablet or phone, you can try Ampd’s Wi-Fi Analyzer to see which of these channels has the least traffic.

Honeywell RTH9580WF Smart Thermostat, showing the WiFi Connection Successful screen. 

Related Posts to How to Fix Honeywell WiFi Thermostat Connection Failure

  1. Fixing Honeywell Thermostat Not Following Schedule Problem
  2. How to Connect Alexa to WiFi, Different Network
  3. Change WiFi Network on Honeywell Smart Thermostat RTH9580WF
  4. How to Fix a DVD that Skips and Freezes
  5. Fixing WiFi Problems on Honeywell RTH9580WF Smart Thermostat
  6. How to Fix Typical Wireless WiFi Router Problems
  7. Echo Dot Quick Fixes, Tips, Problem Solving Help
  8. How to Register Honeywell WiFi Thermostat RTH9580WF Online
  9. Window Air Conditioners Vibrate Wall, How To Fix
  10. How to Reconnect Honeywell Thermostat to WiFi
  11. 12 Volt Power Adapter Failure on External Hard Drive
  12. How to Change Honeywell Thermostat Temperature Setting
  13. Honeywell Thermostat Wiring Color Code
  14. Connect WiFi on Denon S 32 Internet Radio, How To
  15. How to Restart a Honeywell Thermostat

References for How to Fix Honeywell WiFi Thermostat Connection Failure

  1. Why am I Getting a Connection Failure Message, on Honeywell Home

Revision History for How to Fix Honeywell WiFi Thermostat Connection Failure

  • 2019-02-30: Added key phrase targeting, more subheadings, more tags, and fixed several typos.
  • 2019-01-02: Added subheadings.
  • 2017-02-11: Originally published.