Honeywell Thermostat Won’t Turn on Heat [Solved]

If your Honeywell thermostat won’t turn on heat, there could only be a few reasons for this. These include

  • A thermostat that is in delay mode
  • Dying or dead thermostat batteries
  • A heating system that is cut from power
  • A reverse cycle valve that is malfunctioning
  • A furnace that is switched off
  • Issues with thermostat wiring
  • Error with the circuit control board unit
  • Thermostat not positioned in an ideal location
Honeywell thermostat won't turn on heat
A man feeling cold needs heat

The above-mentioned issues are some of the reasons your Honeywell thermostat won’t turn on the heat in your home. Luckily, most of the problems mentioned above, are those you can quickly fix yourself without calling in HVAC professionals. Let’s now go into detail of each of the above issues and their possible solutions.

Read also: Why is my ac thermostat not working?

9 Reasons Your Honeywell Thermostat Won’t Turn on Heat

1) Thermostat In Delay Mode

A thermostat that is in delay mode won’t turn on heat. I assume you have all other settings properly done, and your thermostat is set to heat mode. If your thermostat is in delay mode, the following messages and icons will be flashing on your thermostat display:

  • “Wait” or “waiting for equipment”
  • “Heat” or “Heat on”
  • Fire Icon
  • Sun Icon

If you see any of the above messages or icons flashing or blinking quickly, then compressor protection is on for your heat pump. A heating system can go into delay mode after a compressor shut down or after a power outage. The delay mode protects your compressor from short cycling that could damage your equipment.

Delay mode can take up to 5 minutes. But if you continually see the flashing messages after 5 minutes, there could be another issue with the voltage on your thermostat. In this case, calling an HVAC technician to come and verify voltage is in order.

2) Dying Batteries

Dying batteries could prevent your Honeywell thermostat from turning on heat. If your thermostat is not flashing any ‘heat on’ messages or icons, the problem of your thermostat not turning on heat could be with dying batteries.

Another issue that could help you tell if batteries are flat is a faint display on your thermostat. Your display won’t be as bold as usual.

Typically, your Honeywell thermostat should warn you of low battery for about 2 months before your batteries die entirely. If you missed that message, there is still a solution to resolve this. You can buy any regular AA batteries and replace the old problematic ones.

3) Power Cut Off from Your Heating System

A tripped circuit breaker will cut power to your heating system and heat won’t turn on with your thermostat. After having checked out your thermostat and batteries and there is nothing wrong with them, it’s time to look into the circuit breaker box.

To check the circuit breaker for your furnace, look for a breaker switched labeled FAU or air handler. For your heat pump, look for a breaker switch labeled air conditioner.  A tripped circuit breaker will typically lie in the middle position.

Ensure none of the two breakers (for the furnace and heat pump) is tripped. Reset them where necessary.

Furnace or heat pump turned off

Your furnace or heat pump might have accidentally been switched off. For a furnace, locate the power switch. Usually, this is located near your furnace and looks pretty much like a light switch. Make sure it’s on, if its off turn it on.

For your heat pump system, you can find the power switch outside, usually on the wall of you house.

4) Malfunctioning Reverse Cycle Valve

A reverse valve is a component of your Heat pump system that will switch between the cooling and the heating mode of your heat pump. This functionality makes it possible for your heat pump to work as a heater in the heating season and as an air conditioner in the cooling season.

When you have a defective reverse cycle valve, it will either get stuck in the heat or cool mode. Try running your heat pump in each mode one at a time and see which of the mode isn’t working. If both modes are working, then your reverse valve is not malfunctioning.

However, if any of the two modes is not working, then the problem is a defective reverse cycle valve. The reverse valves are replaceable, call your local HVAC contractor to come and make a full assessment; they will have the problem sorted out in no time.

5)Incorrect Thermostat Wiring

If your thermostat wiring is incorrect, your thermostat will have issues turning on heat. And if they’re loose wires, you need to tug them gently because this will also cause issues with your thermostat.

Very important: For your Honey thermostat to operate heating, it needs the R terminal connected. If you only have Rc terminal connected, take the Rc wire to the R terminal. You can find more instructions here

6) An Error with The Circuit Control Board Unit

A circuit control board that has an error can prevent your furnace from responding to heating and cooling calls from your thermostat.

A circuit control board receives signals from your thermostat about cooling and heating. Then it sends instructions to any other component of your furnace concerned with a specific instruction.

If a circuit control board is not responding, you may need to reset your furnace. You can reset you furnace by turning off the power switch for about 5-10 minutes, then turning it on again. This should reset the circuit control board

Usually, if there is an error somewhere within your furnace, you should see lights blinking. Check the error codes references on the back of our furnace cover.

Read also: Honeywell Thermostat Blank Screen [7 Fixes]

7) Thermostat Not Well Placed

When your thermostat is not placed in a good location, it can not work as you expect it. If you install your thermostat near appliances that produce heat such as stove, it can turn off your furnace even before the temperature you need is reached.

By also avoiding placing your thermostat near windows where direct sunlight can hit it, you can avoid this problem. If sun heat hits on your thermostat, the sensors will think the needed temperature is already reached and your thermostat will send signals not to turn on heat.

Final Thought

If you have solved the problem using these tips, congratulations. If you haven’t, try calling Local HVAC services to come and help. Next time your Honeywell thermostat won’t turn on heat, come back to try out these tips, they might save you a service call.

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