Heating & Cooling

When Should Outside Fans Run on Split Heat Pumps

Hubert Miles | Licensed Home Inspector, CMI, CPI

Published on

Split Heat Pump Outdoor Unit Lg

As we slowly but surely creep towards the end of the cold season, it is becoming more and more common to be curious about how our heating and cooling systems work, and a split heat pump is no exception. You might be wondering when outdoor fans should run on split heat pumps.

Your split heat pump’s fan runs when it’s moving air and turns off when the system is powered off or not moving air. The fan should run if the split heat pump attempts to cool or heat your home. If your split heat pump’s fan is not turning on, a clog or floating debris could be the issue.

This article aims to answer the question as to when the fans on your split heat pump should be running. We also discuss what other signs you may look for when attempting to diagnose a potential problem with your split heat pump and focus on the solutions for said problems.

Traditionally speaking, you wouldn’t want to have a split heat pump as your sole heat source throughout the colder part of the year. 

However, if it is your only option, you may have noticed that your fans have stopped spinning or believe they might have sustained damage while they haven’t been in use.

When Does the Outside Fan Run on a Split Heat Pump?

When your fan should be running, the two primary situations are if the unit is on or actively trying to defrost itself in colder temperatures for use in frigid temperatures. 

The key takeaway from this would be that the fan itself should only be spinning when attempting to cool or heat your home. 

Alternatively, you may run into the opposite of this issue, where your fan is not running at all. 

Should this happen to you, a few different circumstances may have occurred, but for the sake of clarity, let’s go over them below.

Why is the Fan On a Split Heat Pump Not Running?

There are many reasons why the fan on a split heat pump might not run, but below are three of the most likely scenarios.

1. The Fan is Clogged or Has Floating Debris

While there are many different reasons your air pump may not be running, one of the most common occurrences would be the off-hand chance some floating debris or other clogging has gotten into the fan itself and is preventing it from spinning. 

As this is a more simplistic problem, your first solution would be to ensure that the unit is off and has no power.

You will then take a stick or a similar long prodding object and attempt to dislodge whatever is holding the fan in place.

2. The Fan Motor is Failing

A less likely, but still possible scenario would be that your fan motor is failing. If this is the case, you can test your theory by giving your fan blades a push with your selected prod of choice and seeing if the fan motor kicks in. 

Here you come to an impasse of sorts. If the fan does start, you should consider getting a new one, as it is on its way to the junkyard relatively soon. 

If it doesn’t aid the problem in the slightest and your fan doesn’t start, you need a new fan motor as quickly as possible, as your heat pump will not function without it.

While it may come as no surprise to some, using your unit without a working fan can cause severe damage to other portions of the system itself.

These damaging incidents can range from harm to your compressor or any number of other intricate parts within the heat pump itself. If you value your time, money, sanity, or don’t like problems, avoid doing this at all costs.

3. The Device May Need Professional Care

As a final note on why your fan may not be running, sometimes being out of your depth on a repair can happen. In that case, it may be wise to get a hold of a professional to check these problems for you. 

While it may be costly, it beats damaging your heat pump trying to do it yourself, or worse, injuring yourself in the process.

Should the Outside Fan Run When the Heat Pump is On?

New Heat Pump 2 Lg

Your fan should be running without question if your heat pump is on. 

The fan working is primarily due to the outside and inside units working in tandem with one another. 

Knowing this, yes, they should both be working in unison, and if they aren’t, you have some issue with your system and should have it looked at. 

We’ve touched base on a vast majority of the reasons why your fan might not be running while your pump is on. 

Still, another could be something more serious, namely an electric issue, or perhaps a capacitor going out, namely something the inexperienced might not be able to diagnose with a passing glance.

In this instance, stop using your unit and refer to either your manufacturer’s warranty or call for a professional to come out and diagnose the problem for you.

Is the Fan on a Heat Pump Supposed to Run Constantly?

As stated above, your fan is supposed to run as long as you have the heat pump itself on, and again it may be spinning in unexpected intervals to avoid freezing up depending on the climate you are in. 

It’s worth noting that you may hear irregularities in your machine’s operation if you attempt to use it in colder temperatures.

The reason for this is that your heat pump functions by moving more significant amounts of air to accomplish the same job, and for this effort, there is a much more considerable strain being placed upon the machine to achieve the same job. 

For this reason, most people who live in colder areas resort to having two different types of heating solutions in their homes to alleviate some of the pressure on their heat pump when the job becomes too great for the unit to handle.

Reasons a Split Heat Pump Fan Continues to Run

Temporary circumstances aside, there are a handful of other possibilities that may occur which cause your fan to run continuously, regardless of what the temperature is outside, or in some instances, if you’ve ever intended to have the system itself on.

Assuming you know how to operate your unit and have had it for a while, you probably have a decent understanding of when your heat pump needs to be in motion. 

Still, below, we will go over some hypothetical instances where you may have an internal issue at hand.

1. Extremely Cold Temperatures

Cold temperatures are probably the most significant concern you will have to deal with while using a heat pump system. As you’ve probably gathered at this point, will be a vast majority of the problems you can experience in your day-to-day use. 

The heat pump will run tirelessly throughout the cold months to heat your home without finding much success. 

It would be wise to have a backup heating system to keep your system from overwhelming itself. Doing so will save you both time and money.

It is especially true if your area routinely hits freezing temperatures, as the unit may get damaged and leave you to endure those same elements that already claimed your heat pump.

2. Blower Relay Switch Malfunctions

We haven’t touched base on the air handler very much throughout this article, but now we are finally coming full circle with an issue that may affect it, which comes in the form of a malfunction in the blower motor relays. 

If you are unlucky enough for such an issue to occur, you would be on the receiving end of a fan that refuses to quit. 

While this may be an admirable issue initially, the continuous effort of running without limitation will inevitably cause further damage to the motor itself. It will operate without being regulated by the thermostat.

Once again, this probably falls within the umbrella category of being larger than life fix for most normal people, and as such, you will want to have someone with some practical training under their belt to handle the problem for you.

3. Fan Settings

Finally, we have something that almost everyone can handle. Thankfully, you can resolve this issue with a flick of a switch (or a turn of a dial). 

If you find that your fan is simply going on endlessly, one quick check you have at your disposal is looking towards the thermostat.

There is a distinct possibility that you have your unit in the wrong mode. In that case, you may need to change the setting itself from ON, which, as the name might imply, has the unit running non-stop regardless of the situation, to AUTO. Doing so will cause the fan only to operate while your heat pump is in use.

You should note that if you aren’t seeing any discernible difference in the unit’s functionality between the settings being in either the on, or auto function, your thermostat itself may be damaged and need repair. 

Should the Fan Turn On When the Heat is On?

Split Heat Pump Outdoor Unit 2 Lg

It most certainly should be. If you switch on your heat pump, the fan should turn as the two operate alongside each other.

Suppose either one of these units isn’t functioning when it should be. In that case, you have some manner of the issue on your hands that needs resolving so that your unit can once again get back to regulating your home’s temperature into something more livable.

We’ve touched base on a vast majority of the issue that may have caused the fan not to spin when the heat is on, but anything ranging from a build-up of debris inside the fan itself to a short circuit can be the root of the cause.

While on the topic, if the heat pump attempts to cool your home, the fan should be on.

What is Exactly is a Split Heat Pump?

You may be asking yourself, “what does a split heat pump even do” or “what is the difference between a split heat pump and a normal AC unit””?

The primary difference between a split heat pump and your average HVAC unit would be that the divided heat pump functions utilizing two different units.

A split heat unit has an outside unit located outside your home and gathers air to heat up or cool down the house. Then to the second unit, which is lovingly called the air handling unit.

As you might have guessed, the air handling unit lives up to its name by distributing the air the external device has collected throughout the house after the air itself has been cooled by liquid refrigerant or heated with internal compression systems.

The air is then redistributed throughout your home, raising or lowering the temperature depending on your selection.

Final Words

The primary rule of thumb you want to go with is that the fan is supposed to be spinning if your unit is on. 

If for any reason it isn’t, and you couldn’t diagnose it with the above steps, or even if you could find out what is wrong, you don’t trust yourself on the repair, consult a specialist. 

While some people argue about being charged an arm and a leg for repairs, it’s much better than the alternative of losing a finger or two trying to fix something when you are out of your depth!



Hubert Miles | Licensed Home Inspector, CMI, CPI

Hubert Miles is a licensed home inspector (RBI# 2556) with more than two decades of experience in inspection and construction. Since 2008, he has been serving South Carolina through his company, Patriot Home Inspections LLC. As a Certified Master Inspector, Hubert is dedicated to providing his expertise in home inspections, repairs, maintenance, and DIY projects.