3 Reasons Your Heat Pump Fan Is Not Running (+Fix)

A house owner will face several issues with their heat pumps at some point. Some require professional help, while you can fix others on your own. A heat pump not running is a common complaint from most house owners. 

A heat pump does not run due to thermostat issues, tripped breakers, broken reversing valves or capacitors, frozen pumps, or leakages. Potential fixes include correcting the thermostat setting, resetting the breaker, defrosting the pump, and replacing the broken components.  

It is just a brief explanation. This article will explore all the reasons and how to troubleshoot them. If you cannot fix anything yourself, or hesitate to do it, hire a local HVAC professional team to examine the problems and solve them. 

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Why is your heat pump not running?

A heat pump not running could indicate several issues. 

Electricity is one of them. 

A power outage won’t let your heat pump run. 

However, solving the issue is beyond your control. Wait until the power comes back.

Except for that, when a heat pump refuses to run, the problem is related to something else, for example:

You can solve some of them yourself, while others need professional help. 

Let’s explore these causes in detail. 

1. Thermostat issues

When winter arrives, check the thermostat settings before checking the outdoor unit. 

You need to change the setting from COOL to HEAT and then AUTO. 

When you set the temperature to HEAT, the heat pump will start releasing warm air throughout the house.

But if the setting is already in the HEAT option, but your unit does not respond correctly, there might be some other problem with your thermostat:

Incompatible thermostat 

The thermostat you use for your heat pump might be incompatible with your unit. 

All types of thermostats are not designed for heat pumps. 

Some good thermostat models for the heat pump would be:

Dead batteries

If you use thermostats that rely on batteries, you must ensure that the batteries are good and fully charged. 

Faulty batteries will not let your heat pump run, and dead batteries won’t let the unit cooperate in the heating and cooling systems. 

Change the batteries when it runs low or malfunction. 

Most thermostats without a C-wire run by AA or AAA batteries. 

Wrong thermostat wiring

If the thermostat is not wired properly, the heat pump circuit will not receive the signal from the device to run.

As a result, your unit won’t run. 

Incorrect wiring can also fry the heat pump’s components and cause the pump to malfunction. 

Call a professional to check the wires in the thermostat. 

The thermostat is set to emergency heat mode.

When you set the thermostat to emergency heat mode, the system gets the signal to bypass the heat pump. 

The setting will fire up the auxiliary heat part and keep your house warm until your system is repaired. 

The system cuts off the signals to the heat pumps to keep running the electric or gas components.

When your thermostat is set to this setting, it will shut down the refrigeration system, the electric heating elements, and the outdoor fan motor. 

You must reset the normal operation’s thermostat setting to solve the problem. 

A quick thermostat check

To check the thermostat’s condition, perform a quick thermostat testing. 

The test includes setting the thermostat temperature to 5 degrees above or below the room temperature. 

After a few minutes, check the vents for cold or warm airflow. 

The thermostat should be okay if it is blowing warm air.

If not, call a professional to check the thermostat and the air handler. 

2. Power-related issues

Malfunctioning in the electrical systems is another cause behind a heat pump not running. 

 Besides power outages, power-related issues involve fuses and breakers. 

Power switches

Before going to the breakers, check the power switch first. 

All the heat pumps do not have power switches. But if your heat pump has one, ensure it is turned on. 

The switch should be in the cabinet near the air handler. 

Switch on the heat pump and wait for it to run. 

If the pump still does not run, check the emergency switches and turn them on. 

Tripped breakers and blown-up fuses

If your heat pump did not start running after turning on the power switches, it could be due to a tripped breaker or a blown-up fuse. 

If too many heavy appliances are connected to a circuit breaker, it will trip off. 

And if your heat pump is connected to one such circuit, it won’t start due to tripping. 

A heat pump is a heavy appliance, so the tripping may be due to the unit. 

For troubleshooting, you have to reset the breaker. 

To reset the breaker:

  • Turn off the power and go to the breaker. 
  • It will either be in the OFF position or at the center. 
  • If the switch is at the center, flip it to the OFF position, wait for some minutes, and then turn it ON. 
  • If the breaker is in the OFF position, flip it to the ON position. 

Call a professional to replace the fuse if there is a blown-up fuse. 

Make sure it matches the heat pump’s make and model. 

3. Component and unit-related issues

When your heat pump does not run and has no above issues, the problem could be in the components. 

The internal parts, like the compressor, capacitor, valves, condensate pumps, etc., are very important parts of the unit. 

If any part fails to do its job, the rest of the heat pump will start malfunctioning. 

So, it would be best to look into every component’s conditions. 

These parts will need experts for troubleshooting because there might be chances of replacement. 

Dead start capacitor

The start capacitor is responsible for kickstarting the heat pump by sending electrical signals to the motor.

If the capacitor is at fault or dead, it cannot send the signals to the motor. 

Hence, your heat pump will not run. 

You can confirm that the problem is in the capacitor if you hear clicking noises. 

Call your local HVAC team to fix the problem whenever you hear the noise. 

The capacitor may need replacement. 

Faulty reverse valve

The reverse valve ensures that the refrigerant flows in the proper direction. 

It switches the refrigerant direction and allows the heat pump to act as both heater and an air conditioner. 

The heat pump’s mode determines the flow of the refrigerant’s direction.

If the thermostat is set to release warm/cold air, but the heat pump produces the opposite one, the reverse valve is at fault. 

Hire a professional to replace the reversing valve. 

Time delay relay 

A time delay relay is a timer that keeps the current flow from running the coils constantly. 

The relay switch prevents your unit from short-cycling and keeps your heat pump from wearing out. 

If your unit is not starting, the problem might be in the time delay relay. Contact an HVAC to fix it. 

The heat pump switched to the defrost mode while running the heating mode.

It is common to see the outside unit filled with ice in winter. 

If the entire unit is filled with ice, it indicates a problem. 

To eliminate the frost from the heat pump, the unit shuts down the fan motor, turns on the heating elements, and turns the system into cooling mode. 

This confused setting mode in the heat pump will lead to a complete failure of the system. 

The ice in the coils will damage the fan blades and result in compressor failure. 

Call a professional to deal with the breakdown of the unit due to the confusing setting. 

Other causes

The above problems are some of the general issues your heat pump faces and refuses to turn on. 

Other than these, a heat pump not turning on would be due to weather conditions or leakage. 

Frozen heat pump

As I mentioned earlier, it is common for the heat pump to freeze in the winter. 

The heat pumps have a defrost mode setting which helps unfreeze the ice buildup. 

It should melt within 30 to 90 minutes. 

If it doesn’t, the heat pump will not run due to frozen coils and fans. 

It will lead to other issues, like compressor failure. 

Use hot water to defrost your unit. 

Call a professional to fix the unit. 

Avoid using any sharp objects to scrape the ice. 

Frozen evaporator coil and overflowed condensate pan

Check for leakage in the refrigerant lines. 

The leakage in the refrigerant lines will leak the liquid and keep your unit from heating. 

Low refrigerants will not let your evaporator coil have enough heat transfer. 

As a result, the coil will freeze. 

A frozen evaporator coil only happens when the heat pump is in cooling mode. 

The ice will melt and overflow in the drain pan. 

It will further trigger the float switch and stop your heat pump from running. 

Another reason is dirty filters.

The dirty air filters restrict adequate airflow. 

As a result, there won’t be enough heat to be transferred to the evaporator coil, leading to a frozen coil. 

Since the warm air will remain trapped inside the unit, the frozen coil will start melting and overflowing the drain pan. 

You must call a professional if the problem is a frozen coil. 

Clogged condensate drain line

A clogged drain line is another circumstance where the condensate pan overflows. 

The condensation caused by the heating system flows to the condensate pan and escapes through the drain line outside the house. 

If the line is clogged, the water will back up, come back into the unit, overflow the pan, and trigger the safety switch. 

As a result, the unit will shut down and prevent further running. 

The good news here is you can clean the drain line yourself. 

  • Turn off the unit.
  • Locate the condensate drain line. It will be a white PVC pipe located near the outdoor unit. 
  • Find access to the line, pour 1/4th cup of vinegar into the line, and let the solution sit for 30 minutes. 
  • After that, wash the line with normal water. Repeat every month. 

Another method is:

  • Use a shop vac to create a strong connection between the drain line’s end and the shop vac. 
  • Turn on the shop vac for 1-2 minutes and turn it off. 
  • The drain line will be clear. 

Your heat pump should start working after some time. 

If it doesn’t, the clogging may be too high and extensive, or the problem is something else. You need professional help. 

Final thoughts

Check the thermostat settings and tripped breakers if your heat pump does not run. 

If everything is fine, move forward for other issues, like capacitors, reverse valves, frozen heat pump, evaporator coils, and clogged drain line. 

You can clean the clogged condensate lines yourself. 

But if the problem is too extensive or something else, call an HVAC to troubleshoot it. 

Regular yearly maintenance and servicing of the unit can prevent these problems and encourage smooth functioning. 

Why is my heat pump running but not blowing air?

Dirty condenser and air filters, faulty heat pump blower, loose parts, and low refrigerant are some of the major reasons behind a heat pump running but not blowing air. 

How do I reset a heat pump?

Turn off the power and press the reset button or flip the switches. 
The heat pump will have a power switch if it does not have a reset button. Turn it off, wait for 2-3 minutes, and turn it on.

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Arthur Smith

Howdy! I am Arthur Smith, an electrical engineer who is extremely passionate about electronics. I have lived in different parts of the US and currently reside in Wisconsin. I am one of those rare children who knew what he wanted to study and do in life right from the start. I was a curious child who wanted to know how switches work and how the AC works, and I would always observe my dad whenever he would handle the wires and fix things around the house. I currently work as an electrical engineer at a reputed company and write for this blog. And I read loads of books or play video games in my free time.

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