my t9 keeps disconnecting from wifi every few days, i have to reboot it to get it back online.

Diagnosis

The Honeywell Home T9 employs a Wi-Fi chipset that is highly sensitive to "channel hopping" and signal interference. When your router is set to "Auto" for channel selection or bandwidth, it periodically shifts frequencies to avoid congestion. While most modern devices handle this transition seamlessly, the T9 often fails to re-associate with the access point after a channel shift, leading to a "Lost Connection" status on the display. This forces a hard reboot to clear the network cache and re-establish the handshake. Furthermore, the T9 specifically struggles with "Band Steering," a feature where the router attempts to push the device from the 2.4GHz band to the 5GHz band. Because the T9 is strictly a 2.4GHz device, this steering process can cause the router to temporarily drop the connection to the thermostat, eventually resulting in a timeout. You can confirm this is the issue if the thermostat remains connected for several days but drops immediately after a router firmware update or a power flicker in your home.

How to Fix It

To permanently stabilize the T9's connection, you must move away from "Auto" configurations in your router's wireless settings. Follow these precise steps:

1. Access your router's admin panel via your web browser (typically by entering 192.168.0.1 or 192.168.1.1 in the address bar).
2. Navigate to the Wireless Settings or Advanced Wi-Fi tab.
3. Locate the 2.4GHz Band settings. Change the "Channel Width" from "Auto" or "40MHz" to exactly 20MHz. This reduces the bandwidth but significantly increases connection stability for IoT devices.
4. Change the "Channel Selection" from "Auto" to a static channel. Use channel 1, 6, or 11, as these are the only non-overlapping channels in the 2.4GHz spectrum.
5. Check your Security Mode. If it is set to "WPA3," change it to WPA2-PSK (AES) or a WPA2/WPA3 Mixed Mode. The T9 often fails to authenticate with pure WPA3.
6. Disable Band Steering (sometimes called "Smart Connect"). If your router combines 2.4GHz and 5GHz into one SSID, create a separate Guest Network specifically for 2.4GHz devices and connect the T9 to that.
7. Save settings and reboot both the router and the T9 thermostat.

If That Didn't Work

• Install a Wi-Fi Extender or Access Point: If the T9 is located more than 30 feet from the router or separated by dense materials like brick or plaster, the RSSI (Received Signal Strength Indicator) may be too low. Place a 2.4GHz extender halfway between the router and the thermostat to boost the signal floor.
• Assign a Static IP Address: Use the router's DHCP reservation table to assign a permanent IP address to the T9's MAC address. This prevents the connection from dropping when the DHCP lease expires every few days.
• Check the C-Wire Voltage: If the T9 isn't receiving a steady 24VAC from the C-wire, the Wi-Fi chip may brown out to save power for the relay switches. Use a multimeter to verify you have a consistent 24V reading between the R and C terminals. If voltage fluctuates, install a 24V transformer or a C-wire adapter.
• Perform a Factory Reset: Navigate to the thermostat menu, go to Settings > Reset > Factory Reset. This clears corrupted network profiles that may be causing the intermittent drops.

Heads Up

• Avoid placing the T9 directly on a wall that contains heavy electrical wiring or plumbing, as this creates electromagnetic interference that disrupts the 2.4GHz signal.
• Be cautious with "Eco-mode" or "Power Saving" settings on your router, as these can put the 2.4GHz radio into a low-power state that the T9 cannot wake from.
• Always ensure your router firmware is up to date, but be aware that some "Optimization" updates can reset your manual channel settings back to "Auto."
• If you use a Mesh Wi-Fi system (like Eero or Google Nest), ensure "Fast Roaming" is disabled, as the T9 does not support the 802.11r standard and may disconnect during node transitions.