Question 1

my schedule keeps disappearing or resetting to default on its own. why won't it save my changes?

Accepted Answer

DIAGNOSIS The Honeywell Home RTH9585WF relies on a constant stream of 24VAC power to maintain its volatile memory and sync with the Total Connect Home (TCH) cloud servers. When your schedule disappears or reverts to factory defaults, it is almost always due to "power cycling" or "brownouts." If the thermostat is not receiving consistent power via a dedicated C-wire (Common wire), it attempts to "power steal" from the R or Rc wires. During high-demand cycles (like when the furnace blower kicks in), the voltage can drop just enough to trigger a soft reboot. Because the RTH9585WF stores its active schedule in a temporary cache before syncing it to the cloud, a sudden power loss during a write-cycle corrupts the local memory. When the unit reboots, it fails the checksum validation for the user schedule and defaults back to the factory "Standard" template. You can confirm this by checking if the thermostat screen flickers or if the WiFi icon disappears momentarily when the HVAC system engages; this indicates a voltage drop that is wiping your settings. FIX To stop the schedule from resetting, you must ensure a stable 24V power supply and force a hard sync between the hardware and the cloud server. Follow these steps exactly: Verify C-Wire Continuity: Pull the thermostat faceplate off the wall. Locate the C terminal. If no wire is connected, or if a wire is loosely capped, your unit is power-stealing and will continue to reset. If a wire is present, use a multimeter to test the voltage between R and C; it should read between 24V and 28V AC. Perform a Hard Power Cycle: Go to your circuit breaker panel and flip the switch for your HVAC system to "OFF" for exactly 60 seconds. This clears the corrupted cache in the thermostat's internal memory. Clear Local Schedule: Power the system back on. On the thermostat screen, go to Menu &rsa; Schedule. Select "Clear All" to wipe the corrupted local data. Reconfigure via the App: Do not program the schedule on the wall unit. Open the Total Connect Home app on your smartphone. Navigate to the Schedule tab and enter your desired temperatures and time slots here. Force Sync: Once the app schedule is saved, go to the thermostat wall unit, enter the Menu, and select "Sync." This pushes the cloud-based schedule into the local hardware memory, ensuring that even if the WiFi drops, the schedule remains locked in. IF THAT DIDN'T WORK Install a C-Wire Adapter: If your home lacks a C-wire, do not rely on power-stealing. Install a Honeywell C-Wire Adapter (Part #CWE-144) at the furnace control board. This converts the G-wire or a spare wire into a dedicated power source, preventing the voltage drops that cause memory loss. Check the Furnace Transformer: A failing 24V transformer in your furnace can produce "dirty" power with significant ripples. If the transformer is overheating or humming, it can cause the RTH9585WF to reboot randomly. Replace the transformer if it outputs less than 22VAC under load. Update Firmware via Reset: If the schedule still resets, the firmware may be hung. Press and hold the "Reset" button (if available on your specific revision) or remove the unit from the wall and remove the backup batteries for 10 minutes to force a full firmware re-initialization. Check for "Adaptive Intelligent Recovery": Ensure "Adaptive Recovery" is turned off in the settings. Sometimes users mistake the thermostat's attempt to reach a temperature *early* for a schedule change, making it seem like the settings have reverted. HEADS UP Avoid Battery-Only Operation: Never rely on batteries for the RTH9585WF if you have a C-wire option; batteries are for emergency backup, not primary power, and can lead to erratic WiFi behavior. Avoid Frequent Manual Overrides: Excessive manual temperature changes during a scheduled period can sometimes confuse the "Hold" logic, making it appear as though the schedule has disappeared. Check WiFi Signal Strength: A weak signal (below -70dBm) can cause the thermostat to struggle to sync with the TCH server, leading to "ghost" settings where the app shows one thing and the wall unit shows another. Inspect Wire Gauges: Ensure you are using 18-gauge thermostat wire. Using thinner wire over long distances causes voltage drops that trigger the memory resets described above.

Question 2

i replaced the batteries but the thermostat still says 'battery low' and won't let me change settings.

Accepted Answer

DIAGNOSIS The Honeywell Home RTH9585WF is designed to be powered primarily by the 24VAC transformer in your HVAC system via the "C" (Common) wire. While it accepts two AAA alkaline batteries, these are intended strictly as a backup power source during power outages or as a temporary bridge. When the thermostat displays a persistent "Battery Low" warning despite fresh cells, it indicates a failure in the primary power delivery circuit. The device has detected that it is not receiving the required 24V from the wall, causing it to enter a low-power protection mode that locks out user settings to prevent the batteries from draining instantly. This usually happens for one of three reasons: the C-wire is not connected at the furnace/air handler end, the wire has a break or a loose connection at the terminal block, or the 24V transformer has tripped a fuse. Because the Wi-Fi radio in the RTH9585WF is power-hungry, it will deplete standard AAA batteries in a matter of days if the C-wire isn't providing constant current. You can confirm this by removing the thermostat from the wall plate and using a multimeter to check for 24VAC between the R (Red) and C (Common) wires; if you read 0V or significantly less than 22V, the issue is in your wiring, not the batteries. FIX To resolve the power lockout and clear the battery warning, you must ensure the thermostat is receiving constant 24V power. Follow these steps: Shut off the power to your HVAC system at the circuit breaker to avoid blowing the integrated fuse on your control board. Pull the thermostat body straight off the wall plate. Remove the new AAA batteries and set them aside. Inspect the wiring on the wall plate. Ensure the wire in the C terminal is stripped back exactly 1/4 inch, with no frayed copper strands touching adjacent terminals (specifically the R or W terminals). Go to your furnace or air handler. Open the panel to locate the control board. Find the terminal strip and verify that the wire colored to match your thermostat's C-wire is securely fastened to the COM or C terminal. If the wire is tucked back into the wall or not connected at the furnace, the thermostat will never receive power. If you do not have a C-wire, you must install a C-wire adapter kit (such as the Honeywell C-Wire Adapter) or run a new 18/5 thermostat cable. Restore power at the breaker. Snap the thermostat back onto the wall plate. The "Battery Low" message should disappear immediately as the device switches from battery backup to 24V AC power. Navigate to the Menu > Equipment Setup to verify that the device recognizes the power source. IF THAT DIDN'T WORK Check the HVAC Fuse: Locate the purple or amber 3A or 5A blade fuse on the furnace control board. If this fuse is blown, the thermostat will receive no power regardless of the wiring. Replace the fuse with one of the exact same amperage to restore the 24V circuit. Test with a Different Power Source: If you suspect the internal transformer is dead, use a 24VAC plug-in transformer. Connect the two wires from the transformer directly to the R and C terminals on the thermostat wall plate to see if the "Battery Low" error clears. Inspect for "Power Stealing" Issues: Some older systems attempt to "steal" power from the Rh/Rc line. If your system is doing this, the RTH9585WF may struggle to maintain a stable voltage. Ensure the jumper between R and Rc is properly seated or removed depending on your specific heating/cooling configuration. Hard Reset the Logic Board: Remove the batteries and the wall power for 15 minutes. This clears the volatile memory and forces the thermostat to re-poll the power terminals upon reboot, which can sometimes clear a "stuck" battery warning. HEADS UP Battery Quality: Only use high-quality Alkaline batteries. Avoid rechargeable NiMH batteries, as they have a lower nominal voltage (1.2V vs 1.5V), which can trigger the "Battery Low" warning prematurely even when fully charged. Wi-Fi Drain: If you are operating without a C-wire, the Wi-Fi functionality will drain batteries rapidly. Disable the Wi-Fi in the settings if you cannot install a C-wire to extend battery life. Wiring Caution: Never touch the R and C wires together while the power is on; this will instantly blow the fuse on your furnace control board. Terminal Tension: Ensure the push-terminals on the wall plate are clicking firmly. A loose wire in the C-terminal is the most common cause of intermittent power loss and "Battery Low" errors.

Question 3

the touch screen on my honeywell is getting less responsive, sometimes i have to press an icon like 5 times.

Accepted Answer

DIAGNOSIS The Honeywell Home RTH9585WF utilizes a resistive touch interface, which relies on physical pressure to complete a circuit between two layers of the screen. Over time, a microscopic layer of skin oils, household dust, and atmospheric grime accumulates on the surface. Because this specific model lacks the capacitive sensitivity of a smartphone, even a thin film of residue can create a "barrier" that prevents the physical pressure from registering correctly, leading to the "ghosting" or unresponsive behavior where you must press an icon multiple times to trigger a response. Furthermore, this model is prone to static buildup and occasional firmware glitches in the touch-driver layer. If the device has been running for months without a power cycle, the internal voltage thresholds for touch detection can drift. This isn't a hardware failure of the digitizer, but rather a combination of surface contamination and a need for a hard electrical reset to recalibrate the touch sensitivity thresholds. FIX To restore the responsiveness of your RTH9585WF, follow these precise steps to clean the surface and reset the internal logic: Power Down: Do not simply turn off the HVAC system at the breaker. Gently grasp the outer edges of the thermostat housing and pull the unit straight off the wall plate. You will hear a click as the pins disconnect. This ensures no current is flowing through the logic board during cleaning. Surface Decontamination: Use a high-density microfiber cloth. Dampen a small corner of the cloth with distilled water. Avoid using ammonia-based cleaners, Windex, or 70%+ isopropyl alcohol, as these can strip the oleophobic coating on the RTH9585WF screen, making it more prone to smudging in the future. The Circular Wipe: Wipe the screen using small, firm circular motions, starting from the center and moving outward to the edges. Pay special attention to the bezel edges where dust often traps and interferes with the screen's perimeter seal. Dry and Buff: Use a dry section of the microfiber cloth to buff the screen until no streaks remain. Any remaining moisture can cause the touch sensor to register "phantom presses." Hard Reset: While the unit is still off the wall, wait 60 seconds. This allows the capacitors on the board to fully discharge. Reinstallation: Align the unit with the wall plate pins and press firmly until it snaps into place. The system will reboot and automatically recalibrate the touch sensitivity based on the current electrical environment. IF THAT DIDN'T WORK Perform a Factory Reset: If the lag persists, it may be a software glitch. Navigate to Menu > Installer Setup > Reset. Select "Factory Reset." Note that this will erase your WiFi credentials and scheduling preferences, requiring you to reconnect the device to your 2.4GHz network. Check for Voltage Fluctuations: If you have a C-wire (Common wire), ensure it is seated tightly in the terminal. If the thermostat is relying on "power stealing" from the Rh/Rc wires, inconsistent voltage can cause the touch screen to lag or become jittery. Use a multimeter to verify you are getting a steady 24VAC. Update Firmware via App: Ensure your Total Connect Comfort or Honeywell Home app is updated. Check for any pending firmware updates for the RTH9585WF. A firmware patch often optimizes the touch-response timing to fix known "dead zones" on the display. Inspect for Screen Delamination: Look closely at the edges of the glass. If you see a silver or white "bubble" or peeling at the corners, the resistive layer is delaminating. This is a physical hardware failure and requires a full unit replacement as the screen cannot be repaired. HEADS UP Avoid Heavy Pressure: Never use a stylus with a sharp point or your fingernails to press icons; the RTH9585WF is a resistive screen and excessive pressure can permanently dent the touch layer. Avoid Chemical Sprays: Never spray liquids directly onto the thermostat. Liquids can seep behind the bezel and short out the logic board, which is not protected by a waterproof seal. C-Wire Importance: For maximum touch responsiveness and WiFi stability, always use a dedicated C-wire rather than relying on the internal battery or power-stealing circuits. Regular Maintenance: Wipe the screen with a dry microfiber cloth once a month to prevent the buildup of oils that cause the "5-press" frustration.

Question 4

how do i get this thing off the wall plate? i'm afraid i'm going to break it pulling it.

Accepted Answer

DIAGNOSIS The Honeywell Home RTH9585WF utilizes a high-tension snap-fit mounting system designed to prevent the device from sagging over time or being easily knocked loose. Unlike older mercury or basic digital thermostats that slide up or pull straight off, the RTH9585WF is locked into the U-shaped wall plate by reinforced plastic tabs located primarily at the top and bottom of the chassis. The "stuck" feeling you are experiencing is caused by the friction of the plastic clips and the tight tolerance between the display housing and the mounting plate. If you pull from the center or the bottom, you are fighting the tension of the upper clips, which can lead to the plastic tabs snapping or the wall plate being ripped out of the drywall. You can confirm it is properly seated if there is no gap between the outer bezel and the wall; if it is flush, the locking tabs are fully engaged. FIX To remove the thermostat without damaging the internal pins or the plastic housing, follow this specific pivoting sequence: Place your thumb and index finger on the left and right sides of the thermostat bezel, roughly halfway down the unit. Apply a light amount of pressure to the sides to ensure the unit is seated flat against the wall. Locate the narrow gap at the very top of the device where the plastic housing meets the wall plate. Insert your fingertips (or a plastic pry tool/spudger) into the top gap. Do not use a metal screwdriver as it will gouge the white plastic. Gently pull the top edge of the thermostat toward you. You will feel the upper clips disengage first. The unit will pivot outward from the top while the bottom remains anchored. Once the top is angled out at approximately 30 degrees, grasp the sides of the unit and lift it straight up and off the bottom retaining lip of the wall plate. Carefully pull the unit away from the wall, ensuring you do not bend the multi-pin connector that links the display to the wiring base. IF THAT DIDN'T WORK Check for Paint Overlap: If the wall was painted after the thermostat was installed, paint may have seeped into the seam between the bezel and the wall. Use a utility knife to carefully score the perimeter of the thermostat, cutting through the paint layer to break the seal before attempting to pivot the top. The "Side-Squeeze" Method: If the top is too tight to grip, try squeezing the sides of the thermostat housing firmly toward the center. This can sometimes marginally compress the plastic tabs, reducing the friction required to pop the top edge loose. Bottom-Up Leverage: While the top-pivot is the intended method, some units with extreme tension respond better to a gentle push from the bottom. Place your thumb at the bottom center of the unit and apply a steady, upward force while simultaneously pulling the top edge. Verify Plate Stability: Ensure the wall plate itself isn't flexing. If the plate is loose in the drywall, it may be pulling inward as you pull the thermostat outward, creating a "vacuum" effect. Press the wall plate firmly against the wall with one hand while pivoting the display with the other. HEADS UP Pin Protection: Be extremely careful not to touch the gold-plated pins on the back of the display unit; skin oils can cause connectivity issues or "Loss of Communication" errors once reinstalled. C-Wire Verification: If you are removing the unit to check wiring, ensure the C-wire (Common) is securely fastened in the terminal. A loose C-wire is the primary cause of intermittent WiFi disconnects on the RTH9585WF. Avoid Force: If you feel the plastic "creaking" or bowing significantly, stop immediately. The snap-tabs are made of a rigid polymer that will snap cleanly if forced beyond their bend radius. Reinstallation Tip: When putting it back on, align the pins first and press firmly on the bottom edge before snapping the top into place to ensure the pins are fully seated.

Question 5

i'm getting an 'equipment running too long' alert on the screen. what does that mean?

Accepted Answer

DIAGNOSIS The "Equipment Running Too Long" alert on the Honeywell Home RTH9585WF is a protective logic trigger designed to prevent equipment burnout or catastrophic failure. This is not a hardware failure of the thermostat itself, but rather a notification that the thermostat has sent a signal to the HVAC system to run (either heating or cooling) for a continuous period that exceeds the factory-set safety threshold—typically 12 consecutive hours for heating or 6 consecutive hours for cooling. This happens when the system cannot reach the target setpoint. This could be due to external factors, such as an extreme cold snap where the heat pump cannot keep up, or internal mechanical failures, such as a frozen evaporator coil in the AC, a failed capacitor on the outdoor condenser, or a clogged air filter restricting airflow. If the thermostat sees that the temperature hasn't moved toward the setpoint despite hours of operation, it triggers this alert to warn you that the system is working overtime and may be failing. FIX To resolve this alert and determine if your system is failing, follow these precise steps: Clear the Alert: Press the "Cancel" or "OK" button on the thermostat screen to acknowledge the warning. This resets the timer, but it will trigger again if the temperature isn't reached. Verify Setpoint vs. Ambient Temp: Check the current indoor temperature. If the difference between the current temp and your setpoint is more than 5 degrees and the system is running, the system is failing to keep up. Inspect the Air Filter: Remove your HVAC filter. If it is grey or clogged with dust, replace it immediately. A restricted filter causes the system to run longer to move the same amount of air, triggering the alert. Check the Outdoor Unit: Go outside and verify the condenser fan is spinning and the compressor is humming. If you hear a loud buzzing or clicking sound but the fan isn't turning, your start capacitor has likely failed. Inspect Vent Flow: Place your hand over the supply vents. If the air is barely blowing or feels lukewarm during a "Heat" call, you may have a refrigerant leak or a failed heating element. Test the "Recovery" Speed: Set the thermostat to 2 degrees above/below current temp. Note how long it takes to drop/rise by one degree. If it takes more than 60 minutes for a 1-degree change, your system is undersized for the current weather or needs professional service. IF THAT DIDN'T WORK Recalibrate the Temperature Sensor: If the thermostat is mounted near a heat source (like a lamp or sunny window), it may think the room is warmer/cooler than it actually is, causing it to run the system indefinitely. Move any heat sources away or use a remote sensor to average the temperature. Check for Frozen Coils: If this happens during cooling, check the indoor evaporator coil for ice buildup. If you see ice, turn the system to "Off" and run the "Fan" only for 3 hours to thaw the coils. A frozen coil blocks airflow and triggers the "Running Too Long" alert. Verify C-Wire Stability: Ensure the C-wire (common wire) is securely seated in the terminal. Intermittent power delivery can occasionally cause the relay to "stick" in the ON position even if the thermostat tries to turn it off, though this is rare on the RTH9585WF model. Inspect the Heat Pump Reversing Valve: If you have a heat pump and the air coming out is cold during a heat call, the reversing valve may be stuck. Cycle the system to "Cool" and then back to "Heat" to see if the valve snaps back into place. HEADS UP Avoid "Extreme" Setpoints: Setting your thermostat to 75°F when it is -10°F outside may cause this alert simply because your equipment cannot physically reach that temperature. Lower your expectations during extreme weather to avoid constant alerts. Filter Maintenance: Change your 1-inch pleated filters every 30-90 days. Airflow restriction is the #1 cause of this specific alert. Avoid Overriding: Do not repeatedly clear the alert and force the system to run if the house isn't getting warmer/cooler; this can lead to a blown compressor motor or a cracked heat exchanger. Firmware Updates: Ensure your RTH9585WF is connected to strong WiFi. Honeywell pushes background updates that can refine the logic of these safety alerts.

Question 6

the app says my thermostat is offline but the screen on the wall is working fine and shows it's connected.

Accepted Answer

DIAGNOSIS This discrepancy occurs because the RTH9585WF operates on two distinct communication planes: the local control plane and the cloud connectivity plane. When the wall unit shows a "connected" icon, it is confirming a successful handshake with your local wireless router (DHCP assignment). However, the "Offline" status in the Total Connect Home or Honeywell Home app indicates a failure in the WAN (Wide Area Network) tunnel between your router and the Honeywell cloud servers. This "ghost connection" typically happens due to a stale DNS cache in the router, a temporary IP conflict where the thermostat is holding an expired lease, or a firewall rule that has suddenly flagged the thermostat's outbound port (usually port 80 or 443) as suspicious. Because the thermostat's onboard WiFi chip remains linked to the router, the screen doesn't trigger a "Disconnected" alert, even though no data is actually reaching the app. FIX To resolve the synchronization gap, you must force a fresh handshake between the device, the router, and the cloud server. Follow these steps in this exact order: Power Cycle the Network: Unplug the power cable from your modem and your wireless router. Wait exactly 60 seconds to allow the capacitors to discharge. Plug the modem in first and wait for the "Internet" or "Online" LED to turn solid green. Then, plug in the router and wait 3 minutes for the local network to fully stabilize. Hard Reset the Thermostat Connection: On the RTH9585WF wall unit, press the Menu button. Navigate to WiFi Setup and select Disconnect. This clears the current local IP lease. Re-establish Connection: In the same WiFi Setup menu, select Connect. Choose your 2.4GHz network SSID from the list. Enter your password carefully; remember that this model is sensitive to special characters in passwords. Verify Cloud Sync: Once the screen confirms "Connected," wait 2 minutes. Open the app on your mobile device, swipe down to refresh the dashboard, and check if the status changes from "Offline" to "Online." IF THAT DIDN'T WORK Switch to a Static IP: Access your router's admin panel (usually 192.168.1.1 or 192.168.0.1) and locate the DHCP client list. Find the RTH9585WF and assign it a "Reserved IP" or "Static IP." This prevents the router from assigning the thermostat's address to another device, which is a common cause of intermittent app disconnects. Toggle 2.4GHz Bandwidth: The RTH9585WF does not support 5GHz networks. If you have a "Dual-Band" or "Smart Connect" router that merges both bands into one SSID, the thermostat may be attempting to jump to a frequency it cannot maintain. Split your bands into two separate SSIDs (e.g., "Home_WiFi" and "Home_WiFi_5G") and force the thermostat to connect only to the 2.4GHz band. Check DNS Settings: If the device is connected to the router but cannot reach the cloud, change your router's DNS settings from the ISP default to Google's Public DNS (Primary: 8.8.8.8, Secondary: 8.8.4.4). This often resolves routing issues to Honeywell's specific server clusters. Perform a Factory Reset: If all else fails, go to the Menu on the thermostat, select Reset, and choose Factory Reset. You will need to re-add the device to your app account using the MAC address found on the back of the thermostat faceplate. HEADS UP Avoid 5GHz: Never attempt to connect this model to a 5GHz network; it will either fail to connect or will frequently drop the signal, leading to the "Offline" app error. Signal Strength: Ensure your router is not blocked by large metal objects or mirrors between the router and the thermostat, as the RTH9585WF has a relatively small internal antenna. Firmware Updates: When the device is online, do not power cycle it for at least 24 hours. Honeywell often pushes firmware updates silently in the background; interrupting this process can cause a "boot loop" or permanent connectivity failure.

Question 7

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

Accepted Answer

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. FIX To permanently stabilize the connection, you must isolate the 2.4GHz frequency and optimize the router's broadcast channel. Follow these exact steps: Access your router's administration panel via your web browser (usually 192.168.0.1 or 192.168.1.1). Navigate to the **Wireless Settings** or **Advanced Wi-Fi** tab. 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. 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. 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. On the thermostat screen, go to Menu > Wi-Fi > Setup. Select "Forget Network" to clear the old cache. Select the new "Home_Wifi_2.4" SSID and enter your password. 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.

Question 8

my honeywell smart thermostat screen is completely blank, no lights, nothing. it's just dead.

Accepted Answer

DIAGNOSIS The Honeywell Home RTH9585WF is a powered device that requires a constant 24VAC power supply to maintain its WiFi connection and backlit display. Unlike basic battery-operated models, this smart thermostat relies on a "C-wire" (Common wire) to complete the electrical circuit between the HVAC transformer and the thermostat. When the screen is completely blank with no backlight or error messages, it indicates a total loss of power to the RTH9585WF baseplate. This failure typically stems from one of three root causes: a tripped circuit breaker, a blown 3-amp or 5-amp fuse on the furnace/air handler control board, or a missing/disconnected C-wire. To confirm the source, check your HVAC system's air handler; if the indoor blower fan is not running and the furnace power switch is ON, the issue is likely at the breaker or the internal fuse. If the HVAC system is otherwise functioning but the screen remains dead, the issue is isolated to the 24V wiring path between the furnace and the wall plate. FIX To restore power to your RTH9585WF, follow these precise steps to verify and establish a power connection: Gently grasp the thermostat body and pull it straight away from the wall plate. Inspect the wiring terminals. Locate the terminal labeled 'C'. If this terminal is empty, the device cannot power on. Check the wire bundle behind the wall. Often, installers leave an unused blue or black wire tucked back in the wall. If you find a spare wire, strip 3/8" of insulation from the end and insert it firmly into the 'C' terminal. Power down your HVAC system at the breaker panel to avoid blowing a fuse. Navigate to your furnace or air handler. Open the main panel and locate the control board. Find the terminal strip where the thermostat wires connect. Ensure the wire you connected to 'C' at the wall is also connected to the 'C' (or Common) terminal on the furnace board. If no C-wire exists and no spare wire is available, you must install a C-wire adapter (such as the Honeywell C-Wire Power Adapter) or a 24V plug-in transformer. If using a transformer, connect the two wires to the 'RC' and 'C' terminals on the thermostat plate. Restore power at the breaker. Snap the RTH9585WF display back onto the wall plate. The screen should initialize and show the Honeywell logo within 10-15 seconds. IF THAT DIDN'T WORK Inspect the furnace control board for a blown fuse. Look for a small automotive-style blade fuse (usually 3A or 5A) labeled 'Fuse'. If the filament inside the fuse is broken, replace it with an identical amperage fuse. A blown fuse will kill all power to the thermostat regardless of wiring. Check the HVAC safety switches. If you have a condensate overflow pan under your air handler, a clogged drain line can trigger a float switch that breaks the 'R' wire connection to kill power to the thermostat to prevent flooding. Clear the drain line with a vacuum or blow-out tool to restore power. Test for 24VAC power using a multimeter. Set your meter to AC voltage and touch the probes to the 'R' and 'C' terminals on the wall plate. You should read between 24V and 28V. If you read 0V, the issue is the transformer or the wiring run; if you read 24V but the screen is dead, the thermostat hardware itself has failed. Verify the 'R' jumper settings. Ensure the wire from your heating/cooling system is securely seated in the 'R' terminal. If you have separate RC and RH wires, ensure the jumper is configured correctly according to your specific system voltage requirements. HEADS UP Never touch the 'R' wire to the 'C' wire or any other terminal while the power is on; this will instantly blow the 3-amp fuse on your furnace control board. Avoid over-tightening the terminal screws on the wall plate, as the plastic housing can crack, leading to intermittent power loss. If you are using a 24V plug-in transformer, do not connect the 'RH' wire from your furnace; only use the 'RC' and 'C' terminals to avoid voltage conflicts that can damage the WiFi chip. Periodically check that the wires are not frayed or touching each other behind the wall plate, as vibration can cause wires to shift and short out.

Honeywell Home RTH9585WF WiFi Smart Thermostat

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