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Why Does My Heat Pump Blow Cool Air in the Winter? A Phoenix Tech Explains

Arizona doesn’t get cold very often. But when it does, having your heat pump blow cold air is the last thing you need.

So what’s the deal?

There are two possibilities:

  1. Your heat pump is fine, you just think your heat pump is blowing “cold” air
  2. Your heat pump is actually blowing cold air, in which case there is likely an issue with your system

Below, we’ll go into each of these possibilities in more detail, to give you a better idea of why your heat pump is blowing cold air.

Think you may have an issue with your heat pump and want a skilled professional to take a look? That’s what we’re here for. Learn more about the heat pump repair services we offer or…

Possibility #1: Your body is tricking you

We’re not calling you crazy, but hear us out.

Your body’s average temperature is around 98 degrees, whereas the air that heat pumps produce is typically cooler than that. So, even when a heat pump is working just fine, the air a heat pump circulates may feel “cold” compared to your body heat.

Plus, the colder it gets outside, the lower the temperature of the air a heat pump can produce.


Well, heat pumps actually heat your home by absorbing heat from the air outside, drawing that heat inside, and using that heat to warm up your home’s air.

The colder it gets outside, the less heat your heat pump can absorb from outside, and the lower the temperature your heat pump produces.

While this may seem like an issue, your heat pump can usually heat your home just fine, but when it’s extremely cold out (below 30 degrees), it just takes your system a little longer to do so.

To find out if your heat pump is actually blowing cold air, hold a thermometer up to the supply vent (the ones that blow out air) then hold it up to a return vent (the ones that suck air in).

The air coming from your supply vent should be anywhere from 15-30 degrees hotter than the air near your return vent (depending on how cold it is outside).

Possibility #2: Reasons your heat pump is actually blowing cold air

If your heat pump is blowing cold air, some possible causes include:

  • Low refrigerant levels
  • Problems with the reversing valve
  • Thermostat accidentally set to “cool” mode
  • Fan set to AUTO
  • Dirty outdoor unit
  • The system is in a defrost cycle

Let’s look at each of these in a little more detail below.

1. Low refrigerant

Refrigerant is the substance that absorbs heat from the air outside and draws that heat into your home. If there is a leak in your refrigerant line, there won’t be enough refrigerant to draw in the proper amount of heat to warm up your home’s air.

If this is your issue, you’ll need to contact a professional to come to check out your heat pump. Refrigerant circulates in a closed-loop system, so if your system is low on refrigerant, there's a leak. A pro will need to repair the leak as well as refill your refrigerant.

2. Reversing valve issues

The reversing valve is the mechanical valve that switches your heat pump from cooling mode to heating mode. If there is an issue with your reversing valve, your heat pump may actually be in cooling mode, in which case the air coming from your vents will be cold, not warm.

To fix this, you’ll need to contact a technician and have them take a look at your system.

3. Thermostat set to COOL

Don’t worry, it happens more often than you think. If you recently turned your heat on, this could be the issue. Check your thermostat and make sure that its set to HEAT, not COOL.

4. Fan set to AUTO

Another setting on your thermostat is your FAN setting. This setting should be set to AUTO, not ON. When set to on, your heat pump will blow air whether it’s heated air or not. When set to AUTO, your heat pump will only blow air when it’s heated.

5. Dirty outdoor unit

As we mentioned above, your heat pump heats your home by drawing in warm air from outside. However, your heat pump will struggle to absorb warmth from outside if the coils on the outdoor unit are dirty, clogged or blocked with debris (resulting in less heated air to your home).

To determine if this is your issue, go outside and take a look at your outdoor unit (compressor). If it looks like the one pictured above, it’s time to enlist a professional to come and clean it.

6. The system is in a defrost cycle

If it gets too cold outside, your heat pump’s outdoor unit may freeze, causing your system to go into defrost mode.

When in defrost mode, your heat pump starts transferring heat out of your home (towards your outdoor unit) instead of transferring heat inside your home. This transfer of warm air to your outdoor unit helps to melt any ice on your outdoor unit.

When this happens, your heat pump is essentially in “cooling mode,” which is why you may feel cold air coming from your vents. Once your outdoor unit has defrosted, your heat pump will return to transferring heat into your home rather than to your outdoor unit.

If your heat pump is blowing cold air, look outside and see if your outdoor unit is frozen or has frost on it. If so, your heat pump is likely in defrost mode and you don’t need to call a technician. However, if your heat pump doesn’t return to heating mode and you’re noticing cool air for a long period of time, you should reach out to a professional.

If you want to learn more about the heat pump defrost cycle, check out our blog, “Heat Pump Defrost Cycle

Think you have an issue with your heat pump?

If you’re trying to determine whether the cold air you’re feeling is a legitimate heat pump issue or not, we suggest you do the following...

1) Test your heat pump’s supply and return air with a thermometer. If the air from the supply vent is around 90 degrees, your heat pump is working fine.

2) If you test your home’s air supply and find that your heat pump is blowing cold air, call and schedule an appointment with a professional who can fix your heat pump.

Not sure who to call to help with your heat pump? We are Arizona’s most trusted HVAC pros and we’d be happy to help you repair any heat pump issues you’re facing.