Honeywell Thermostat Blowing Cold Air on Heat Setting [Fixed]

Last updated: May 20, 2023

It’s nearly wintertime and the heating season is just around the corner. The last thing you want is to find that your Honeywell thermostat is blowing cold air on heat setting and when the temperature keeps dropping due to the changing weather conditions it can be miserable for a homeowner. 

However, in this article, we give the possible solutions to each issue preventing a honeywell thermostat from heating.

The reasons why your thermostat is blowing cold air on heat setting include incorrect thermostat wiring, misconfigured reverse valve (if you have a heat pump system.)  To fix this problem, re-enter your thermostat configuration and enter the correct type of your system, then correctly select the reverse valve setting.

Read also: Honeywell Thermostat EM Heat Explained

Honeywell thermostat wiring

5 Possible Reasons a Honeywell thermostat is blowing cold air on heat mode

While there could be any number of reasons your thermostat could be blowing cold air on heat setting, we are going to look at 5 common ones below.

1)      Incorrect thermostat wiring

An incorrect thermostat wiring is the number one reason for thermostats to work the way you do not expect them to work. Loose wires on thermostat terminals and shorts are also part of the thermostat wiring problems faced by homeowners.

Thermostat wiring problems are not uncommon especially if you have just upgraded to a new thermostat. Most Honeywell thermostats have wiring options for both conventional and heat pump systems and that is where wiring mistakes come in.

Also read: 7 wire honeywell thermostat wiring diagram

Firstly, find out what kind of system you have. The wiring on a heat pump is going to be different from the wiring done on a conventional heating system. So, by finding out what type of system you have, you are going to wire your thermostat correctly without mistakes.

Read also: Honeywell thermostat not blowing cold air

How do you know what type of system you have? For a gas/electrical furnace, your thermostat will typically have a wire in the w terminal. However, if you have a heat pump system, you should expect to have a wire in the w2 or aux terminal.

2)      Incorrectly Configured Reverse valve

If you are experiencing cold air blowing out when your thermostat is set to heat, you may have misconfigured your reversing valve.

  Go to your thermostat settings and switch from heating to cooling. Set the temperature about 2 degrees lower than the current temperature reading. Feel the air that comes out of the vent. Is this air cool or warm?

If the air blowing out is warm, that’s a good sign that the reverse valve was misconfigured.

 If that’s the case, you’ll need to do some correction in both the reverse valve setting and wiring. Follow in these steps.

Step 1. Go to the thermostat configuration and enter the correct system type and change the reversing valve setting.

Step 2. Remove the thermostat cover from the wall and don’t forget to take a snap of the current wiring (you may need to restore your wiring to the current one.)

Step 3. Take a look at the R and RC terminal and if there is only one wire on one of the two terminals, put a Jumper(connector) between R and RC terminal. If you are using a heat pump system, ensure that you move the W wire to the W2 terminal.

Read also: Furnace Running But Not Blowing Air [Fixed]

3)      No power to your furnace/ HVAC system

Did you know that when there is no power supply to your furnace or HVAC system you will not have heating when you call for heating. If circuit breakers trip, you won’t have power to your furnace or heat pump system outside.

To ensure power is getting to your system, check the breakers that control power to your HVAC system and restore them where necessary.

But not only breakers can cut power to your HVAC system. Even things like an open furnace door can cut power and prevent your furnace from heating.

Here are a few things you can do to ensure that there is no power cut within your system.

1)      Ensure that panels or doors of your HVAC systems are not closed. Most of the system doors have a safety switch feature that prevents your system from turning on when doors are left open.

2)      Also make sure that there are no blown out fuses on the control board of your furnace. The control board can be found in the inside of your furnace.

3)      Check the wires on the terminal block of your furnace and match them with ones that are on another end near your thermostat.

Other things you can do to diagnose the heating/cooling problem is use a multimeter to measure voltage on the RC and R and between any other wire in your thermostat.  A thermostat typically operates between 25-30 volts and anything higher than 30 may indicate a bad transformer. On the other hand, anything lower than 20 may indicate a short somewhere.

In this case, you may want to call a professional for help.

Read also: Sensi thermostat blowing cold air on heat

4)      Bad Furnace control board

An HVAC control board receives heating and cooling instructions from your thermostat and then relays them  to other parts accordingly. Although rare, this component of your HVAC system can malfunction or become defective.

However, the good news is that control boards are replaceable. Just make sure you call a professional to do all the hard work for you.

5)      Incompatible thermostat

Not all newer thermostats can work with older HVAC systems. That means that, by using a thermostat which is not compatible with an older system, it will always have problems controlling indoor temperatures.

This mainly applies to newer smart thermostats. Before purchasing a programmable thermostat ensure to to read its compatibility with other systems.

See also: Nest thermostat blowing cold air on heat


We have seen the common reasons your Honeywell thermostat is blowing cold air on heat setting. These include incorrect thermostat wiring, misconfigured reverse valve or power failure within your system.

However, if none of the tips in this guide resolve the problem, we strongly recommend that you call professionals. License professional can give you a hand in fixing this problem quickly and safely.

Thank you for reading.



How to fix Nest thermostat not heating

Similar Posts