Heat Pump Outside Unit Not Running? Easy Troubleshoot Guide

If you have a heat pump system that provides both cooling and heating, it is highly likely that you have encountered technical failures a number of times. So what do you do when your heat pump outside unit not running? It is always recommended that you seek help from a qualified technician to fix your heat pump problems, however being able to diagnose and repair common problems in your heat pump system can come in handy when your systems breaks down unexpectedly and may save you loads of case.


There are various reasons why your heat pump outside unit will stop running:

  • The Thermostat not sending the signal to heat or cool.
  • Power related problems
  • The heat pump is in defrost while in heating mode.
  • The thermostat is in emergency heat mode
  • The Thermostat not sending the signal to heat or cool

Check the thermostat selections and ensure you have set them to the desired settings. To test if the thermostat is working correctly, adjust the thermostat heat setting 5 degrees above the room temperature, wait for a minute or so, and then check whether there is warm air being blown out of the vents. If there is warm air, the thermostat is okay, but if not, it is likely to be faulty.

Power Related Problems

In case of a power surge, your heat pump system might have tripped a circuit breaker or blown a fuse thus cutting power. This can be easily repaired by replacing the blown fuse. Moreover, go to your circuit breaker switch and check whether any of the switches have flipped; switch is off and then restart it once more.

The Heat Pump is in Defrost While in Heating Mode

During winter it is common to find the outside unit of the heat pump covered in in light ice and frost and this does not affect the working of the pump. However, if the entire unit is covered with snow and ice, this is an indication of a problem. The extreme cold impends the normal operation of the heat pump by preventing transfer of heat between outside air and the refrigerant. To get rid of this frost, the heat pump shuts down the outdoor fan motor, turns on your heating elements and also sets the system into cooling mode. This confused state leads to failure of the system and may damage your heating system beyond repair. Further, the ice in the coils can cause extensive to damage the fan blades, sensitive fins, and cause compressor failure.

To fix this:

• Melt the ice using water from a hose; do not try to chip the ice using a hard or sharp object because it may damage the coils.

• Unclog the unit by removing snow and debris.

The Thermostat is in Emergency Heat Mode

When the thermostat is in this mode, it shuts down both the refrigeration system and electric heating elements, which leads to shutting down of the outdoor fan motor. To fix this, reset the thermostat to normal operation.


It is important to note that this guide is not a substitute for routine maintenance on your system; you should have professionals carry out routine maintenance on your system to prevent future break downs and also extend the lifespan of your system. Moreover, this guide cannot provide all of the solutions for all pump problems, thus if the situation looks serious, seek help from a professional.

Related Article: Outside AC Unit Not Running But Inside Is

Written by

Rene has worked 10 years in the HVAC field and now is the Senior Comfort Specialist for PICKHVAC. He holds an HVAC associate degree and EPA & R-410A Certifications.
Share Your HVAC Quote/Cost

Share Your HVAC Quote/Cost

We rely on readers like you to share your HVAC system cost or quote. It really helps other visitors to estimate the cost of a new HVAC unit.

ie: Tranx XR13, Lennox xp15
Include Ductwork Replacement? *

Leave a Comment

DMCA.com Protection Status