The first thing you should check if your heat pump is blowing cold air in the winter is your thermostat settings. You need to ensure that your thermostat is set to “Heat” and the fan is set to “AUTO.” If your fan setting is set to “On,” your heat pump will blow air, whether heated or not.
The heat exchanger uses coils to transfer heat from the ignited gas to the air. When cold air blows from a furnace the heat exchanger, furnace burner, or exhaust are likely the cause. This may be due to dirty components, broken parts, or the many safety mechanisms within the gas system.
Incorrect thermostat settings can prevent the system from initiating the heating mode. Ensure that your thermostat is set to the heating mode with the desired temperature. Additionally, malfunctioning thermostat sensors can miscommunicate with the heat pump, preventing it from entering the heating mode.
If your heat pump is on but not blowing hot air, it could be due to a dirty air filter, low refrigerant levels, or a malfunctioning thermostat. The outdoor unit may also be iced over, or the reversing valve may not be working properly. Contact a professional for further inspection.
First, check to make sure the thermostat is set correctly. You will want to make sure that the fan control is set to auto, and not 'on'. If the thermostat appears set correctly, turn off your heater at the thermostat and check the filter. If the filter is dirty, replace it.
Luckily, the solution is simple. Clean off your heat pump and clear away any debris that may be blocking the way. Air filter is dirty: Air filters are put in place to catch dirt and debris, but when too much builds up, it can block airflow to the compressor, the part of the unit that actually heats the air.
One of the most common reasons for the heat pump to blow warm air in cool mode is incorrect thermostat settings. This happens when you erroneously set the thermostat yourself. Another reason for this is when someone tampers with the thermostat after you have set it to cooling mode.
First, make sure that the heat pump's air filter is clean. If it's heavily clogged, change it for a fresh one and then see if the heating returns to normal. (Change the filter regularly, every 1 to 3 months.) As for other possibilities: The issue could involve thermostat malfunctions.
One of the most common reasons your HVAC is not heating could be due to incorrect thermostat settings. Make sure your thermostat is set to “heat” or “auto” and the temperature setting is raised. Sometimes, a faulty thermostat can cause the HVAC heating to be blowing hot air intermittently.
Simply reset the thermostat to AUTO. What causes the heater fan to emit cold air is the ON switch allows the fan to operate even when heat isn't required to maintain temperature control. Checking the pilot light and seeing if it is out could be a quick fix also. If the pilot is out you can try relighting it.
To check this in the heating mode, compare the temperatures of the suction line from the outside to the suction valve at the bottom. If the difference is more than 3°F, the valve needs to be changed. In cooling mode, check both reversing lines the same way you did for heating mode.
Check the thermostat
Maybe your heater is not blowing hot air even though the fan is running. As a result, any air that blows out of the vents while your heater is off will usually feel cold. In such a case, there could be an easy solution, particularly if your thermostat setting is the problem.
In addressing why your heat pump is blowing cold air, causes include a dirty unit, a clogged filter, and the wrong thermostat settings. And that's why maintenance is important.
The HP reversing valve is a small component in a heat pump with a big job. It's a brass valve located at the outside unit and connects to the refrigerant lines inside the condenser unit cabinet. It's also connected to the thermostat and controls the refrigerant flow.
Low Refrigerant
However, if there's a refrigerant leak or the refrigerant level is too low, the heat pump won't be able to efficiently absorb and transfer heat, resulting in inadequate warmth. A professional HVAC technician is equipped to identify any leaks and recharge the refrigerant to the appropriate levels.
Two thermostat issues that could cause your furnace to blow cold air include (1) your thermostat is still set to COOL, not HEAT and (2) your thermostat fan is set to ON, not AUTO.
If you notice ice starting to build up on your system, it's a clear sign that the refrigerant is low. The refrigerant absorbs heat, so the coils will start to develop ice if there isn't any refrigerant to do that. Some heat pumps will also start to go into defrost mode if there isn't enough refrigerant.
To address this issue, make sure your unit has adequate clearance around it, and remove any snow or ice gently with a stream of warm water. If you continue to have this problem, call a professional HVAC technician to inspect and repair your heat pump or add more insulation.
Issues with the pilot light, high limit switch, blocked burners, leaky ductwork, electrical problems, and blower motor failures are common reasons for HVAC systems blowing cold air. These problems often require professional maintenance and repairs.
In many cases, something as basic as replacing expired thermostat batteries, tightening loose sensor wires, or upgrading failing circuit board components restores immediate comfort control and coordinated equipment functionality, avoiding improper heating events coinciding with air conditioning mode attempts.
You Probably Have a Stuck Reversing Valve
This is the most common culprit of a heat pump that won't switch modes–a stuck or broken reversing valve.
Blocked or closed air vents can restrict the airflow in your home, preventing warm air from reaching the rooms. Check all vents and registers to ensure they are open and unobstructed. Additionally, inspect your ductwork for any obstructions or leaks that could hinder heat distribution.
A bad thermostat can be detected when your AC or furnace is not turning on, your HVAC systems are not turning off, the thermostat not responding, your HVAC system is short-cycling, the room temperature not matching the temperature displayed on the thermostat, and the programmed setting resetting themselves.