How to fix aux heat on thermostat

How to Fix the Aux Heat on the Thermostat. It maintains the temperature indoors when the outdoor temperature is dropping. When you observe the indicator of the aux heat on your thermostat, it simply tells you that after reaching the desired temperature, the heat pump of your thermostat requires help.

It turns on automatically when the temperature goes toward 2 degrees and gets below the required temperature when the temperature is reached, it immediately turns off to prevent the problem of extra heat. It would be best if you kept cleaning the clutter from dirt and dust. Also, clean or replace according to the requirement of the heat pump filter of the thermostat. Not use the emergency heating setting for the use of standard sets.

How to Fix Aux Heat on Thermostat

The aux heat turns on when the heat from outside is not transforming properly to heat pump from outside air. This condition reaches when the outside temperature is about 30-40 degrees, and the inside temperature should be 3 degrees cooler than the thermostat’s temperature.

The aux heat is not bad; it is not the same in working with the furnace when it gets cold. The heat pumps of the aux in the thermostat are heat strips whether the outside temperature is getting out. In the summer season, the unit requires refrigerant, but it can not transfer the heat when the level is low.

The system approaches the heat setting when the heat pump is not generating enough heat to give warmth to your home so that the heat pump can be in defrost mode. The aux heat is 50 % more costly than the conventional heat. The expenses over the aux vary, which relies on the energy provider.

Working on Heat Pump

The heat pump transfers heat between locations for cooling and heating. It takes the heat energy from outside in the colder month and warmth your home. And it uses the heat from within the house to chill your home by releasing it outside. The parts of heat pumps are inside air handling uni and outside condensing units. The heat pump can be able to change or reverse the valve.

On the inner side of the air handler, there is a heating element on it. Relying on the model of your pump, the functions of the heating elements are auxiliary heat and emergency heat.

Auxiliary Heat

The electric resistance heating element is turned on using the supplementary heat. Depending on the heat pump’s model, the extra heat’s capabilities might be slightly different because some pump models require the emergency mode the heat pump transfers heat between locations for cooling and heating.

The thermostat automatically turns on the auxiliary heat when the desired temperature does not reach after 5,8 or 10 to 20 minutes. Some thermostats’ temperatures are set to be handly while others are pre-programmed with the temperature level on which it turns on.

The auxiliary heat will be only shut off in the case when the required temperature reaches. When the Auxillary heat stays long, it signals something wrong.

  •   Turning on the Aux Heat

You will learn about turning the aux heat when lifting the “aux heat “ on the thermostat.

 Reasons to Turn on the Thermostat’s Aux Heat

  •   Cold Weather

The aux heat turns on in the cold weather. And it is expected to turn on the aux heat at the cool temperature, especially when it is under 40 degrees. The heat pump is the essential element of the thermostat. Still, when the temperature goes under 40 degrees, the heat pump loses little of its efficiency.

That’s why it will lead to the most problem with indoor temperature. And this is because the heat pump cannot extract the suitable heat energy from outside to warm up your home. Whenever the set temperature reaches the auxiliary heat, the heat pump gets shut off.

When the thermostat’s temperature rises 3 degrees or more, the auxiliary heat will turn on.

  • Defrost Mode of the Aux Heat

When the defrost mode gets activated, it relies on the backup heat to give your home warmth. That’s why when the heat pump is in defrost mode; you must use the auxiliary heat properly.

The Time Limit of the Auxiliary Heat

The auxiliary heat runs as long as the temperature is set on your thermostat. It would be best if you took into your note when the aux heat is displaying many times in a day or a whole day, the aux heat can appear whenever your turn on the system.

The long period of staying in the aux heat means there is an issue with the heat pump. Turning on the aux heat can be referred to as the malfunctioning of the heat pump.

Fixing your Aux Heat Thermostat

You can not wholly avoid the aux heat coming on in the northern areasThe heat pump transfers heat between locations for cooling and heating. Still, when temperatures are below 40 degrees, the heat pumps struggle to get enough heat from outside to warm your house correctly.

  •  Keeping the Temperature of the Thermostat Low

The main reason for mostly appearing the auxiliary heat is that the temperature is too high. So when the temperature is set high, the aux heat will turn on to keep your home warm. When the outside temperature is below 40 degrees, there is no way for your heat thermostat to give warmth to your home.

  •  Maintenance of the Heat Pump

You can reduce the malfunction of the heat pump with the help of Maintainance. The loose wires on the damaged reversing valve can cause many problems. But with the heating maintenance, you will get rid of the high utility bills and get cold at night.


When the heat is not producing, it may be due to the reversing valve or the low level of the refrigerant. You should also observe the other issues like blocking with ice in the venting system and building up the dirt. You should maintain your HVAC system.

You should make the schedule to inspect the system to check whether anything is getting wrong or not; if the system has any fault, then you must have to resolve it like turning on the aux heat can be fixed with the above procedure.

Leave a Comment