Honeywell Heat Pump Troubleshooting

In the tables below you can find the list of possible troubles which you can encounter using your Honeywell heat pump. The information given there may be helpful in case of your heat pump not working properly.

The types of defects or breakdowns are various. There are detailed descriptions of possible problems and causes of heat pump not cooling or heat pump fan not spinning. Here you can find some questions which give you the idea what to investigate or to check before addressing to the specialists.

The Honeywell heat pump flash codes given in the tables and their descriptions are meant to give you the key to the possible problems you have with your heat pump. Do not try to do any repair if you are not a specialist!


SymptomPossible CauseAction
Display will not come on.Thermostat is not being powered.• Check that C terminal is connected to the system transformer.
• Check for 24 Vac between C and R terminals.
— If missing 24 Vac:
— check if the circuit breaker is tripped—reset the circuit breaker.
— check if the system fuse is blown—replace the fuse.
— check if the power switch on the HVAC equipment is in the Off position—set to the On position.
— check wiring between thermostat and HVAC equipment—replace any broken wires and tighten any loose connections.
— If 24 Vac is present, proceed with troubleshooting.
Thermostat microprocessor is locked up.Remove the thermostat from the wallplate for 2 minutes. After 2 minutes, replace the thermostat on the wallplate.
Temperature display is incorrect.Room temperature display has been reconfigured.Enter Installer Setup number 37 and reconfigure the display.
Thermostat is configured for °F or °C display 3 .Enter Installer Setup number 14 and reconfigure the display.
Bad thermostat location.Relocate the thermostat.
Temperature settings will not change. (Example: Cannot set the heating higher or the cooling lower.)The upper or lower temperature limits were reached.Check the temperature setpoints:
• Heating limits are 40 to 90°F (4.5 to 32°C)
• Cooling limits are 48 to 99°F (7 to 35°C).
The setpoint temperature range stops were configured.Check Installer Setup numbers 34 and 35 and reconfigure the setpoint stops.
Heating will not come on.No power to the thermostat.• Check that C terminal is connected to the system transformer.
• Check for 24 Vac between C and R and between R and Y1 terminals.
— If missing 24 Vac:
— check if the circuit breaker is tripped—reset the circuit breaker.
— check if the system fuse is blown—replace the fuse.
— check if the system switch at the equipment is in the Off position—set to On position.
— check wiring between thermostat and HVAC equipment—replace any broken wires and tighten any loose connections.
— If 24 Vac is present, proceed with troubleshooting.
Thermostat minimum off time is activated.Wait up to five minutes for the system to respond.
System selection is not set to Heat.Set system selection to Heat.
Cooling will not come on.No power to the thermostat.• Check that C terminal is connected to the system transformer.
• Check for 24 Vac between C and R and between R and Y1 terminals.
— If missing 24 Vac:
— check if the circuit breaker is tripped—reset the circuit breaker.
— check if the system fuse is blown—replace the fuse.
— check if the system switch at the equipment is in the Off position—set to the On position.
— check wiring between thermostat and HVAC equipment—replace any broken wires and tighten any loose connections.
— If 24 Vac is present, proceed with troubleshooting.
Thermostat minimum off time is activated.• Wait up to five minutes for the system to respond.
• Enter Installer Setup number 33. Reconfigure minimum off time (if required).
System selection is not set to Cool.Set system selection to Cool.
System on Indicator (flame=heat, snowflake=cool) is displayed, but no warm or cool air is coming from the registers.Heating equipment Is not operating.Verify operation of heating equipment In self-test.
System on indicator is not displayed, but heating or cooling system is operatingOption not activated.Enter Installer Setup number 36 and reconfigure to 00.
Outdoor temperature not displayedOption not activated.Enter Installer Setup number 24 and set to 01. Thermostat must have OT terminals and a C7089B1000 installed.