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Is your heat pump not blowing hot air like it should but instead blowing cold air? Don’t worry, it’s not unusual for a heat pump to blow cold air when it’s on heat. There’re many reasons your heat pump could be blowing cold air.
These could be any of the following issues, your heat pump is in defrosting mode, your thermostat settings, the refrigerant is leaking, a dirty outdoor unit, the circuit breaker is tripped, or leaky ductwork.
I shall be discussing these and many other issues shortly in this article. And because I hate to leave you with no solutions, I have also provided DIY tryouts on each of the potential causes.
Why is My Heat Pump Blowing Cold Air?
When you first turn on your heat pump, it’s very normal for it to blow cold air than warm air. This happens more often when the cold air trapped in the ductwork is flushing out but soon the warm air should start coming out of your vents.
Other times your heat pump will blow cold air when your outdoor unit is covered in ice or snow. It will start defrosting your outdoor unit by going into defrost mode. In defrosting mode, it will temporally blow cold air to warm up the coils in your outdoor unit and melt away the ice and snow.
Defrosting typically takes up to 10 minutes, and if your heat pump continues blowing cold air beyond 10 minutes it could be a sign of any of these issues.
While there could be several reasons why your heat pump is not blowing cold air, the following are the most common ones:
- The reverse valve is in heating mode (sometimes stuck there)
- Bad thermostat wiring
- Dirty air filters
- Heat pump outdoor unit not turning on
- Leaking refrigerant
Read also: Heat Pump Not Turning On [4 Easy Solutions]
1. Reverse Valve Issues
A reverse valve that stays or gets stuck in the heating mode will prevent your heat pump from cooling or blowing cold air into your home. A reverse valve or changeover valve is a device in your heat pump system that reverses the direction of the flow of the refrigerant.
The direction of the flow of the refrigerant determines whether your heat pump is cooling or heating. And this gives it the functionality to work both a heat pump and an air conditioner.
When you turn on your thermostat and you change the mode from cooling to heating, the reverse valve accordingly changes the direction of the refrigerant. The other way around happens when you change from heating to cooling.
How can I fix a reverse valve that is not working?
If you think your heat pump’s reverse valve is not working or is stuck in one operating mode, start by first checking if your thermostat is switched to cooling mode.
And if it’s not, set it to ‘cool’ mode and wait to see if the cold air will start blowing out of the vents.
If you are using a Honeywell thermostat you will most likely need to remove the face of your thermostat to see a button for switching between heating and cooling.
And if you are using a Nest thermostat, you’ll need to swap the orientation between O and B in your thermostat’s settings. If your current orientation is on B change it to O, then turn on your thermostat. Wait for a few minutes to see if the cold air will start blowing out of the vents.
2) Bad Thermostat Wiring
An incorrect thermostat wiring could also negatively affect how your heat pump works. If you recently had your thermostat installed, it’s likely that there is something wrong in your thermostat wiring.
Typically, a heat pump thermostat will have an O/B terminal. This terminal controls the changeover valve. If the O/B terminal is not connected or is loosely connected, switching between the cooling and heating modes will be a problem for your heat pump.
How do I fix a bad thermostat wiring?
If you have a thermostat that is not correctly wired, this problem can be fixed pretty quickly. Depending on the model and make of your thermostat, you’ll need to remove your thermostat from the wall and check the wiring behind it.
TIP: If you are working with wiring, you should turn off your system on the circuit breaker. This is for your safety and that of your system.
Once your thermostat is off the wall, ensure that there are no loose or hanging wires. Ensure also that the R and the Rc terminals are connected to wires. If there is only one of these two terminals which is connected, ensure that there is a short wire(jumper) between them.
Rc is power for the cooling terminal and if it’s not connected, your heat pump won’t cool.
3) Dirty Air Filters
Actually, when your heat pump is not cooling your home and your thermostat has the correct settings, the first thing you need to check is the status of your air filters.
Dirty and clogged air filters always cause problems with the normal working of your heat pump. The EPA recommends that air filters should be replaced once or twice in two months. But again, this can depend on the quality of your surrounding air and how often your system works.
What happens if you never change your air filter?
- They will restrict the amount of airflow into your indoor handler. And this will in turn restrict airflow to the evaporator coils.
- If the airflow is restricted to your evaporator coil, then, only a little air will be cooled. And this can stop your heat pump from blowing enough cold air.
- Clogged air filters will allow dirty air and other substance to bypass it and build up on the evaporator coil. This will cause ice formation on the surface of the evaporator coil and can cause the leaking of water.
- And if the evaporator coil has lots of build-up on it, the surface area for cooling the air will reduce and this will also prevent your air handler from blowing cold air.
How to tell if your air filter is dirty
If you don’t remember the last time, you had your heat pump air filters replaced, then it’s high time you did so.
Air filters are typically found at the return vents or at your heat pump’s indoor unit (air handler cabinet)
Open the return registers and remove the filter. Take a look at the air filter and if its color is like that of mud, then it’s definitely clogged and needs a replacement.
However, before getting a new filter, take note of the size of your air filter. Once you get a new one, insert it, and don’t forget to put back the cover.
How to change a furnace air filter
- Make sure you turn off your furnace. You can do this at the furnace power switch, circuit breaker, or thermostat
- Locate the air filter. If it is located right at your furnace, remove the access panel by pulling down the latch. If your air filter is located behind the return duct the procedure is pretty much the same.
- Once you have access to the air filter, pull it out and check its condition. If it is dirty, you need to change it.
- Check the size of the filter that your heating system uses. It should be in this format 20*25*1. The size tells you the dimensions and thickness of the air filter. The last number,, in this case, 1 tells you about the thickness of your filter. The 1- 2-inch filter needs replacement every 1- 3 months. The 3–4-inch type needs replacement every 6-9 months.
- Once you have a new filter place it into position making sure you take note of the direction of airflow. The arrow on the filter should be away from the door.
- After you are done, close the access panel or vent cover before turning on your heater.
4. Heat Pump Blows Cold Air: Leaking Refrigerant
Have you checked the reverse valve, and everything looks great? There is one possible reason your heat pump is still blowing cold air on heat. That is, the refrigerant is too low or leaking.
Sometimes leaks can develop within your HVAC system and this could cause the refrigerant to escape. And, when it does escape, your HVAC system will not blow hot air when put on the heat mode and neither will it blow cold when put on the cooling mode.
This is because Heat pumps do not generate heat as furnaces do. Instead, they use refrigerant to transfer heat from the cooler side to the warmer side.
It works by absorbing heat from your indoor air as it passes through the evaporator coil. Then releasing the heat outside as it passes through the condenser coil of your heat pump outdoor unit.
The Fix? If you think your system might be running low on refrigerant. Call in a technician to come and take a look.
5. Blocked Outdoor Unit
Heat pumps usually are installed with an outdoor unit and an indoor unit. The outdoor unit has a coil and a fan, and the indoor unit has a coil and a fan too.
In the heating mode, the outdoor unit will work as the evaporator and the indoor unit as the condenser.
So, if the outdoor unit(evaporator) is covered with debris or leaves, it won’t be able to absorb much heat energy. Because of that, the heat pump will blow cold air.
The Fix? Make sure that the outdoor unit is always kept free of objects such as leaves, dirt, or even snow and ice. If your outdoor unit is covered with grass, you can blow the grass away. if there is ice covering it, you can pour hot water on it to melt down the ice. This is an easy fix that should get your heat pump back on track quickly.
6. Outdoor Condenser Not Turning On
Another reason your heat is not blowing cold air is that your outdoor unit could be off. If the condenser is off, there won’t be heat transfer from your home to the outside air.
Check if the breakers are tripped or not. Locate the breaker for the heat pump outdoor unit usually labeled ‘air conditioner’. If it’s tripped, reset it accordingly and if it’s not tripped, go out and check if the condenser unit is running.
If breakers are not tripped and your condenser unit still can’t turn on, look at a small device called the disconnect on your wall (near refrigerant lines). Does it look intact? If it’s pulled out, then power can’t reach your condenser unit. To fix this, try putting back the disconnect in its position. This should restore power to your condenser.
If there is no noise coming from your condenser unit then the problem most like has to do with power.
The Fix: If the outdoor unit is not working. Check the circuit breaker panel and look out for the outdoor unit breaker. If it has tripped, reset it. This should start your outdoor unit. If the breaker keeps on tripping, it could be a sign that there is a problem with your HVAC system or its safety measure.
7. Leaks in Your Ductwork
You could be getting cold air from vents when your heat pump is on heat because there are leaks in your ductwork.
The ductwork of your heating system moves the warm air throughout your living spaces. The ducts are usually installed outside the area that is not heated. Because of that, they may be exposed to extreme weather conditions and at times they may have leaks on them or disconnections in their joints especially if they were not installed properly.
Another cause for leaky air ducts is rodents. If these find their way into your attic, they can bite and cause damage to your ductwork.
When you have leaky ducts, the hot air that your furnace generates will be escaping from the air ducts before reaching your home and the cooler air will get in, (there will be a mix.) Because of that, the air that will make it into your home will not be as hot.
The Fix. If you think you have leaky air ducts, you can seal them off using duct tape (metallic duct tape is more effective than any other duct tape). If it’s something that you can’t fix yourself, call HVAC professionals to come and help.
8. Thermostat Settings
- Make sure that you check the thermostat settings. Sometimes, you can accidentally change your thermostat settings. When your thermostat is on ‘on’ your heater won’t blow hot air but cold.
Solution: Make sure that you change your settings to auto or heat.
- Another common mistake among homeowners is the setting on the fan. If your fan is set to on, it will continue blowing cold air when your furnace is on break.
Solutions: If the fan setting is set to ‘on’ change it to auto or heat. Your furnace should stop blowing cold air
- And if your thermostat uses batteries to operate, check if your battery is low or dead. A dying battery can affect how your thermostat works. It can cause your thermostat to send false temperature signals to your furnace.
- Solution: If the battery is low or dead, change the battery to bring your heater on.
How To Keep Heat Pumps In Good Working Condition To Avoid Issues
There are a few things that you can do to keep your heat pump working optimally and efficiently. These include:
Changing air filters on time
Filters should not work for more than 3 months before changing them.
If you have pets around your home, you can change them even once a month.
Observing Regular Maintenance
To keep your heat pump working in great condition, the Government recommends that you observe regular HVAC tune-ups at least twice a year. This not only keeps your system working at optimal, but it also prevents unforeseen breakdowns which can be costly.
Keeping Your Condenser Unit Clean
Your heat pump outdoor unit also known as the condenser helps with disposing of heat from your home. It has a network of coils where the gaseous refrigerant changes to liquid as it releases the heat.
Over time dirt, leaves, and other objects can build up on your condenser unit making it hard for it to dispose of heat. This can cause your unit to run longer and inefficiently to try and cool your home.
How do you reset your heat pump?
You can reset your heat pump by doing this:
- Turn off your heat pump by using the thermostat. Then switch it off by using the power switch
- Go into the breaker panel and switch off the breaker for both the outdoor and the indoor unit
- Wait for about 5 minutes before turning on everything back in reverse order.
Can a heat pump run without freon?
A heat pump cannot run without freon (refrigerant). A refrigerant is needed in a heat pump to transfer heat from the outside air to the inside of your home. And it also works in reverse when you need cooling in your home. A heat pump that has leaked or no freon would
- Not provide any heating or cooling for your home
- If your heat pump is not recharged for a long, this could damage your air compressor, bringing in more costly repairs.
Do heat pumps lose Freon over time?
A heat pump does not lose freon no matter how long it is used. A refrigerant can only escape if there is a leak within its path. If you suspect a leak in your refrigerant, call in an HVAC technician who can come and verify the refrigerant charge.
Why is my heat not coming through the vents?
If heat is not coming out through the vents in 1 or two rooms, you might have closed or blocked registers. Sometimes registers can be closed accidentally. You need to make sure you open them all. Move away any objects placed near them such as furniture, and rugs. These might be blocking the hot air from freely circulating into your room.
How long should a furnace run?
How long a furnace should run during a heating cycle depends on many factors. But on average, a heating cycle can take anywhere between 10 to 15 minutes.
How do I know if my furnace flame sensor is bad?
You can only know if your furnace flame sensor is bad if you inspect it. If the sensor insulation is missing, you might need a replacement. If the sensor insulation is intact but has lots of soot buildup, you might just need to clean it up.
To clean your flame sensor, you’ll need to use sandpaper or steel wool. Gently rub the rod with it until it looks clean enough. When you are done cleaning it, use a piece of cloth to wipe out the rod.
How often should you change the flame sensor?
You can expect to change newly installed flame sensors in about 5 to 10 years.
Final Thought on Heat Pump Blowing Cold Air
There are countless things that can negatively affect how your heat pump works. But when your heat pump blows cold air, go through these tips we have provided before calling an HVAC technician.
However, I do recommend you have an HVAC maintenance tune-up twice a year. In the spring and fall. Change filters, and let the HVAC technician examine all other parts of the furnace.
Regular maintenance of your heater will not only keep it running efficiently, but it will also prevent unforeseen breakdowns which can be more costly in the future.
HVAC tech with over 30 years of experience. Retired and doing repair work on the side around Madison County, AL.