Picture of the Honeywell RTH9580WF thermostat, displaying the Select Wi-Fi Network screen, showing the wireless signal strength meter with a full strength signal.

Troubleshooting Honeywell Thermostat WiFi Problems RTH9580WF

We’re explaining common Honeywell WiFi thermostat network problem troubleshooting, as experienced on our Honeywell RTH9580WF internet controlled thermostat, although this information applies about as well to Honeywell’s other wireless thermostats, including the RTH8580WF, VisionPRO TH8320WF, VisionPRO 8000, et al.

Troubleshooting Honeywell WiFi Thermostat Connection Lost Issues

By this, we mean that the thermostat will not connect to your home Wi-Fi network. It may or may not have been able to connect prior. Typical causes for this type of failure to connect are listed next.

1.1 Wi-Fi Network Not Found in Scan

Your wireless network does not show up in the list of in-range networks that the thermostat discovers during a Wi-Fi scan during initial setup.

Solution: Make sure your wireless router is powered up and that your WiFi SSID is not hidden (being broadcast).  Most routers broadcast the network name SSID by default.  However, you may have purposely hid your SSID for security purposes.  If so, then your network will not appear in the in-range networks list when the thermostat scans for available networks.  So you’ll have to 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.
Honeywell RTH9580WF thermostat, displaying the Select WiFi Network screen, with the Other… option highlighted.

1.2 Wi-Fi Network Settings have Changed

That is, the access point password, network name, or network security settings may have changed.  This often happens when you buy a new router, one that has a different default wireless network name and password.

Solution: Determine your correct Wi-Fi network name and password, and then 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 Router Needs Rebooting

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.

Solution: Restarting the router clears out working memory, and allows the router to start again from a known-clean point.  Rebooting a router / access point often restores proper router operation.

1.4 Interference Stopping Good Wi-Fi Connection

Most Honeywell wireless thermostats communicate using the 802.11g Wi-Fi standard.  Transmissions adhering to this protocol occur in the 2.4 Ghz. frequency range.  Now 2.4 Ghz. is also a popular frequency region for many devices, including other Wi-Fi networks as well as non Wi-Fi devices such as cordless telephones, microwave ovens, baby monitors, Bluetooth speakers, and home theater system remote controls.  There’s a lot of traffic in that band therefore, particularly in crowded apartment buildings or closely spaced housing.  So occasionally, your wireless thermostat may fail to connect or to maintain connection with your router due to interference from nearby devices like these operating.

Solutions: Eliminate the source of the interference if possible.

Try turning off any cordless telephones in your house and see if the problem goes away.  If so, replace your phones (including the base unit) with a wireless phone that operates on different frequencies than 2.4 Ghz.  Many of the newer wireless phones operate in the 1.9 Ghz. band, which are specifically designed not to interfere with WiFi communications in the home.  But don’t buy one if you’re not sure what frequencies it operates on.

Do similarly with other wireless devices as well.  Try turning them all off and see if the problem disappears.  Then, turn them each back on, one by one, and observe the reaction of the thermostat after each.  If the thermostat connection goes bonkers after you power up a particular device, then that’s likely the one causing the interference.  Try moving this appliance further away from the thermostat and router.

Reposition your router closer to the thermostat.

1.5 Thermostat Too Far Away from your Wireless Wi-Fi Router

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: Relocate the router closer to the thermostat.  Or, try the solutions in problem 1.4 above.

1.6 Defective or Misconfigured Router / Wireless Access Point (WAP)

Verify this 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.

Solutions: 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.

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.

1.8 Defective Thermostat

If none of the above causes turns out to be true, your thermostat may indeed be defective.  Over time, most electronic components, including those of the Wi-Fi radio in the thermostat, weaken and fail to perform as well as they did when new.  The transmission power of the thermostat 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 (24 X 7) contact with the Honeywell Total Comfort Connect infrastructure on the internet.

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

1.8 Defective Furnace

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 will likely fail.

Solution: 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.

Troubleshooting Honeywell WiFi Thermostat Keeps Losing Connection Problem

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 Went Down

Solution: Try accessing the internet through another device on the same Wi-Fi network as your thermostat.  If they do not work either, then notify your internet service provider about the problem, and wait for service to return.

2.2 E02 and E43 Error Messages 

Some Honeywell thermostats display E02 and E43 errors when the Wi-Fi connection has been lost or cannot be initiated due to the reasons discussed above. 

Solution: Execute items in the first major section above to troubleshoot this problem.

2.3 Router Lost Power

Perhaps your wireless router has been disconnected from mains power.

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

2.4 Modem Lost Power

In some installations, the cable / DSL modem and router access point are not in the same box.  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: Check the status lamps on the modem, router, and wireless access point to verify operation.  Any red or blinking lights could indicate a problem.

Check that you can connect to your network with other wireless devices, as described in items 2.1 above.

2.5 Honeywell Total Comfort Connect Servers May be Down

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

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

2.6 Wi-Fi Channel Too Busy

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.

Solution: 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.

Related Posts


Revision History

  • 2017-03-14: Originally published.