Honeywell Thermostat Troubleshooting

Below, you can check out the list of troubleshooting instructions for different models of Honeywell thermostat brand. The guidelines are present in the form of tables for you to navigate them easier. Just find the technical issue, check out the possible causes, and fix it up. A wide range of technical problems provided starting from heat emission failure and finishing by WiFi programming issues. Besides, you can also find the error alert codes – it will help you to identify the type of failure quickly. Note that some problems require installer’s help.

Honeywell CT3200 Thermostat Troubleshooting

If...Then...
Display does not come on• Make sure the batteries are fresh and installed correctly.
• Set System switch to Off. Remove batteries and insert backward for five to ten seconds to reset thermostat. Replace batteries correctly: display should come on.
Temperature display does not go lower than 45°F (7°C) or higher than 88°F (31°C) during programming.• Temperature limit setting is reached: range is 45°F to 88°F (7°C to 3TC).
Display shows flashing "bAt Lo."• The batteries are low; replace them as soon as possible.
• If ‘bAt Lo’ continues to display after replacing batteries, set System switch to Off and insert batteries backward for five to ten seconds. Replace batteries correctly; display should come on.
Temperature change occurs at wrong times• Check program times for period in question. Be sure AM and PM indications are correct. Make sure current day and time are correct. Reprogram if necessary.
Heating does not come on• Check that the System switch is set to Heat.
• Check the system fuse or circuit breaker and replace or reset if necessary.
• Check for correct wiring and good connections.
• If the display is blank or displays "bAt Lo" install fresh batteries.
• Allow time for the furnace to heat up and the fan to come on before checking for heat at the register.
• If temperature setting is higher than current room temperature and SYSTEM ON arrow is displayed, thermostat is operating correctly. Contact heating contractor for assistance.
Cooling does not come on• Check that the System switch is set to Cool.
• Check the system fuse or circuit breaker and replace or reset if necessary.
• Check for correct wiring and good connections.
• If display is blank or says ‘bAt Lo,’ install fresh batteries.
• The thermostat has a built-in time delay on cooling. Allow 5-10 minutes after changing setting before air conditioner starts.
• If temperature setting is lower than room temperature and SYSTEM ON arrow is displayed, thermostat is operating correctly. Contact ac contractor.
The house is too warm or too coolPress RUN PROGRAM to check the current temperature setting. If desired, change the temperature setting.
Furnace cycles too often or system cycle length is too short or too long• Adjust the screws on the back of the thermostat.
The thermostat current setting does not match the display temperature to within plus or minus 1°• Plug the wiring hole in the wall behind the mounting plate with insulation to prevent drafts that might adversely affect thermostat operation.
• Be aware that it is normal for the current setting and the displayed room temperature to differ on occasion.
• During recovery from setback or setup, setting and displayed room temperatures can differ for up to 30 minutes after recovery period.

Honeywell RTH6500WF-Wi-Fi-Series Thermostat Troubleshooting

Error CodeAction
E01 During Wi-Fi Setup, the router lost power.• Ensure your router has power.
• If trying to connect to a hidden or manually added network, confirm the router has power and is working.
E02 Invalid Wi-Fi password. This code displays for 30 seconds, then the thermostat will re-enter Wi-Fi Setup mode.• Re-enter password for your home Wi-Fi network.
• Repeat setup process and confirm your password for your home Wi-Fi network.
E42 Router is not issuing an IP address to the thermostat.• Wait for 30 minutes, connection can take several minutes.
• If still no connection, remove thermostat from wallplate for 10 seconds, then reconnect it
• Verify your router is correctly setup to automatically give IP addresses.
E43 No internet connection. Thermostat cannot communicate to Total Connect Comfort.• Make sure the Internet cable is plugged in.
• Reboot the router.
E99 General errorRemove thermostat from wallplate for 10 seconds, then reconnect it

Honeywell CT2700 Thermostat Troubleshooting

SymptomPossible CauseCorrective Action
Heating/cooling equipment will not operateNo AC power to thermostat.Check power to heating/cooling equipment:
— On/Off switch
— Fuse or circuit breaker
— Loose 24V connection: At thermostat; at fumace/air conditioner
— Incorrect wiring: check appropriate wiring diagram.
System switch on thermostat in wrong position.Reset System switch.
Thermostat minimum-off times operating for cooling.Wait five minutes
Incorrect wiring.Check wiring.
Heating/cooling equipment inoperative.Consult equipment manufacturer instructions.
Partial displayInoperative thermostat.Replace thermostat.
Still in installer setup mode.
No displayNo power to thermostat.Check power to thermostat.
Thermostat mounted incorrectly on wallplate.
Temperature display is incorrectThermostat is configured for °F or °C.Reconfigure the display.
Cannot change temperature settingThe upper or lower temperature limits were reached.Check the temperature setpoints; temperature setting range is 40°F (4°C) to 99°F (37°C).

Honeywell Y9420S Thermostat Troubleshooting

SymptomPossible CauseRemedy
ST9420C has a blank LCD displayNo power to the heating system.Check that there is power to the heating system.
Fault in ST9420CCall Installer
ST9420C indicates that Heating and/or Hot Water are ON. but radiators are cold and/or taps are running with cold water.Temperature controls are switched off or set too low.Check that the temperature controls in the system are set to appropriate levels.
Boiler or other system controls have malfunctioned.Call Installer
ST9420C shows the message: ‘INTERNAL FAULT'Fault in ST9420CCall Installer
Every few seconds, the ST9420C screen shows the message: SERVICE DUE 28daysST9420C is counting down the number of days until your next boiler service is due.Arrange a boiler service before the counter reaches zero.
After servicing your boiler, the Service Engineer / Installer will reset the ST9420C to remind you when the next boiler service is due. Each service is normally a maximum of 1 year apart.
Although the heating is still operating, the ST9420C screen keeps flashing the message: SERVICE DUEYour boiler service is overdueArrange an immediate boiler service.
After servicing your boiler, the Service Engineer / Installer will reset the ST9420C to remind you when the next boiler service is due. Each service is normally a maximum of 1 year apart.

Honeywell BDR91T Thermostat Troubleshooting

ProblemSolution
How reliable is 2-way RF communication?The 2-way RF communication (also known as wireless communication) used by Honeywell is extremely robust and reliable. When installed correctly the Signal Strength test feature allows the Installer to locate the system components where mutual signal reception is strong. During communication, signals are sent several times to ensure receipt, and if any message is garbled, the error detection software recognises this and ensures the message is repeated again.
What do I do if RF communication is lost?The most likely cause for loss of communications is the DT92E batteries running low on power. This will be indicated on the DT92E display by a flashing battery symbol, or the display may even be blank. Simply replace the batteries and wait a few minutes for communications to become re-established.
If this does not resolve the problem it may be that the RF signal path between the ST9420C and the DT92E is blocked by a metal object. Check the direct path between the two devices and reposition any object that may be blocking the signal, or move the thermostat
How do I know when to change the batteries in the CS92A cylinder sensor?If the CS92A batteries need changing, the ST9420C will show the message “SENSOR LOW ВАТТ" and the tap symbol will flash. You can confirm this by pressing the CS92A button, whereupon the red light will give a brief flash every second to indicate a low battery state. It is important to change the CS92A batteries as soon as the low battery condition is indicated, as reduced battery power may affect the RF signal strength and impair RF communications
How do I know when to change the batteries in the DT92E room thermostat?If the DT92E batteries need changing, the battery symbol will flash on the DT92E display. DT92E will continue to operate for at least 4 weeks after the indicator begins to flash. The ST9420C will also show the message 'SENSOR LOW ВАТТ' and the radiator symbol II11II will flash. It is important to change the DT92E batteries as soon as the low battery condition is indicated, as reduced battery power may affect the RF signal strength and impair RF communications

Honeywell AQ1000TP2 Thermostat Troubleshooting

Error Solution
LOThe temperature measured by the thermostat is below the thermostat's display range
HIThe temperature measured by the thermostat is above the thermostat's display range
ERThe thermostat has lost communications with the AQ2000 control panel
--The thermostat might be defective. The floor sensor may also be defective if the thermostat has been configured for F mode. Cooling or heating has stopped
Floor When the thermostat has been configured for AF mode, floor will flash if the floor sensor is defective or not installed. The thermostat will still control the ambient air temperature but will ignore the floor temperature limits

Honeywell 69-0568 Thermostat Troubleshooting

ProblemSolution
Display flashes during operationProgramming has been lost because of a power outage. You must reprogram
Program is lost due to power outageCheck that backup batteries are installed correctly. Replace if necessary. Reprogram the thermostat
Temperature change occursCheck the program times for the period in question. at the wrong times. Be sure that AM and PM indications are correct. Make sure the current day and time are correct. Reprogram if necessary.
If using Programmed Recovery, remember that the furnace or air conditioner comes on before the WAKE and RETURN start times so the house will be at the desired temperature when the period starts.
Display flashes during programmingYou have reached the temperature setting limit. The setting range is 45° F to 88° F. In models with automatic heat-cool changeover, the COOL temperature setting must be at least 3° F above the HEAT temperature setting
Display will not come onCheck that heat or cool system power is on. If you use batteries,
Make sure thermostat is correctly mounted on base
Display says HEAT ON or system light is on, but no heat is coming room the registers.Allow time for the furnace to heat up and the fan to come on before checking for heat at the register
The house is too warm or too cool.Press PRESENT SETTING to check the current temperature setting. - If desired, change the time or temperature setting
Cooling will not come onCheck the fuse or circuit breaker and replace or reset if necessary, if display is blank or says REPL BAT, install fresh batteries.
Check that switch on thermostat is set to COOL or AUTO.
The thermostat has a buitt-in time delay on cooling to protect the compressor. Allow up to 10 minutes after changing the setting before the air conditioner starts.
If temperature setting is lower than current temperature, and display says COOL ON, contact your heating and air conditioning contractor
Heating will not come one.Check the fuse or circuit breaker and replace or reset if necessary, if display is blank or says REPL BAT, install fresh batteries.
Check that switch on thermostat is set to HEAT or AUTO.
If temperature setting is higher than current temperature, and display says HEAT ON, contact your heating and air conditioning contractor

Honeywell Enviracaire Elite HE225A Thermostat Troubleshooting

ProblemWhat to Look forWhat to Do
Low humidityFurnace blower not operating.•Reset circuit breaker or replace fuse.
•Check that the furnace power is on.
•Check all external wiring connections.
•Check humidity control setting.
•Call a heating contractor.
Rapid air changes. Drafts (cold air is dry and is an added load to humidifier).•Keep doors and windows closed.
•Close fireplace damper if not using.
•Minimize exhaust fan running time.
•Seal around doors and windows.
High humidityCondensation on walls.•Turn off humidity control and water until condensation is completely evaporated.
Heavy condensation on windows.•Turn humidity control low enough to eliminate bath and cooking condensation moisture. If moisture persists, more ventilation is needed.

Honeywell T8095A-191108AJ Thermostat Troubleshooting

ProblemCheckAction
No heat.—system switch. May be in OFF or COOL position.Move system switch to HEAT position.
—fuse or circuit breaker.If blown or tripped, replace fuse or reset breaker.
—furnace power switch. May be OFF.Move switch to ON .
—pilot flame. May be out.Relight pilot flame according to furnace manufacturer’s instructions.
—thermostat connections.Turn OFF power to furnace. Check for correct terminal hookups. Repair any frayed or broken wires. Firmly tighten all terminal screws. Turn on power.
Energy savings temperature program 12 hours off.—program dial for proper day or night phase.Turn clock ahead 12 hours. Move minute hand clockwise only.
Rooms do not warm up at programmed time.—timer program for heating system. May need more time to warm up rooms.Move red pin one-half hour earlier on the program dial.
Temperature change occurs at the wrong time.—program pins for correct time locations.Relocate pins to desired settings.
Room temperatures are not correct.—positions of thermostat set point levers.Reset to desired temperatures.
—position of sub base system switch (heating-cooling model).Move to desired operating position.
Room temperatures are not correct (continued).switch at COOL, move temperature setting levers 5° F [3° C] below room temperature. Cooling system should start. If the system does not operate, call a qualified service technician.
Bumer on time too short.—anticipator setting. Increase anticipator setting by 0.05. Observe burner operation.
Bumer-on time too long.—anticipator setting. Decrease anticipator setting by 0.05. Observe burner operation.
No cooling. —system switch. May be in OFF or HEAT position.Move switch to COOL position
—fuse or circuit breaker.If fuse is blown or breaker tripped, replace or reset.

Honeywell 9000 Thermostat Troubleshooting

ProblemSolution
Display is blank• Check circuit breaker and reset if necessary.
• Make sure power switch at heating and cooling system is on.
• Make sure furnace door is closed securely.
“Wait” appears on the screen• Compressor protection feature is engaged. Wait 5 minutes for the system to restart safely, without damage to the compressor.
Heating or cooling system does not respond• Touch SYSTEM to set system to Heat. Make sure the temperature is set higher than the Inside temperature.
• Touch SYSTEM to set system to Cool. Make sure the temperature is set lower than the Inside temperature.
• Check circuit breaker and reset if necessary.
• Make sure power switch at heating and cooling system is on.
• Make sure furnace door is closed securely.
• If “Wait” is displayed, the compressor protection timer is on. Wait 5 minutes for the system to restart safely, without damaging the compressor