why does my thermostat keep disconnecting from wifi? i have to keep re-adding it in the app.

Diagnosis

The Honeywell Home RTH9585WF frequently drops its connection due to a combination of strict 2.4GHz band requirements and sensitivity to "signal noise" or interference. This specific model lacks a 5GHz radio, meaning it relies entirely on the 2.4GHz band. If your router uses "Band Steering" (where 2.4GHz and 5GHz share the same SSID), the thermostat often attempts to handshake with the 5GHz signal, fails, and then drops the connection entirely, forcing a manual re-add in the TotalConnect Comfort or Resideo app. Furthermore, the RTH9585WF has a relatively small internal antenna. If there are dense materials between the router and the thermostat—such as foil-backed insulation, brick, or large mirrors—the signal-to-noise ratio (SNR) drops. When the signal strength dips below -70 dBm, the thermostat's wireless chip enters a power-save mode that often fails to wake up correctly, resulting in the "Offline" status you see in the app. You can confirm this by navigating to the thermostat's physical screen: Menu > Wi-Fi > Network Status. If you see "Poor" or only one bar of signal, the hardware is physically struggling to maintain a heartbeat with the router.

How to Fix It

To permanently stabilize the connection, you must isolate the 2.4GHz frequency and optimize the router's broadcast channel. Follow these exact steps:

1. Access your router's administration panel via your web browser (usually 192.168.0.1 or 192.168.1.1).
2. Navigate to the **Wireless Settings** or **Advanced Wi-Fi** tab.
3. Disable **Band Steering** or **Smart Connect**. Create two separate SSIDs: one named "Home_Wifi_2.4" and another named "Home_Wifi_5". This prevents the thermostat from attempting to connect to the incompatible 5GHz band.
4. Change the 2.4GHz Channel from "Auto" to a fixed channel. Use either **Channel 1, 6, or 11**. These are non-overlapping channels and significantly reduce interference from neighboring networks.
5. Set the Channel Width to **20MHz** instead of 40MHz. While 40MHz is faster, 20MHz is much more stable and penetrates walls better for IoT devices like the RTH9585WF.
6. On the thermostat screen, go to Menu > Wi-Fi > Setup. Select "Forget Network" to clear the old cache.
7. Select the new "Home_Wifi_2.4" SSID and enter your password.
8. Wait 60 seconds for the "Connected" checkmark to appear on the screen before opening the app to verify the status.

If That Didn't Work

• Assign a Static IP Address: DHCP lease expiration can cause the RTH9585WF to lose its IP and fail to reconnect. In your router's "LAN Settings" or "DHCP Server" section, find the MAC address of the thermostat and assign it a permanent, static IP address. This ensures the router always knows exactly where to send data packets to the device.
• Install a Power Extender Kit (PEK): If your thermostat is flickering or disconnecting, it may be a power issue rather than a signal issue. If you do not have a C-wire (Common wire) providing constant 24V power, the device relies on "power stealing," which can cause the Wi-Fi chip to brown out. Install a C-wire adapter or a PEK to ensure the thermostat has a steady current.
• Deploy a Dedicated 2.4GHz Access Point: If your router is more than 30 feet away, a standard extender often introduces too much latency. Instead, use a wired Access Point (AP) placed halfway between the router and the thermostat to provide a clean, strong signal.
• Disable Firewall "MAC Filtering": Ensure your router's security settings are not blocking new MAC addresses. Some high-security routers see the RTH9585WF's reconnection attempts as a "spoofing" attack and blacklist the device. Add the thermostat's MAC address to the "Allowed" or "Whitelist" section of your firewall.

Heads Up

• Avoid placing large metal objects or mirrors directly in the line of sight between the router and the thermostat, as these reflect 2.4GHz signals and create "dead zones."
• Whenever you change your router password, you must manually "Forget Network" on the thermostat before adding the new credentials to avoid a credential conflict.
• Keep your router firmware updated; many manufacturers have released patches specifically to improve compatibility with legacy 2.4GHz IoT devices.
• If the device continues to drop after a static IP and channel fix, check the wiring behind the wall plate to ensure the R-wire and C-wire are seated firmly in their terminals.