Ever walk into your house and realize the heat pump just isn’t doing its job?
The air feels wrong, the thermostat says it’s running, but when you peek outside, the big unit is totally quiet. Frustrating, right?
The outdoor part of your heat pump is the powerhouse that keeps your home comfortable, so when it stops, the whole system is basically down for the count.
The good news is that a silent outdoor unit doesn’t always mean an expensive repair.
Sometimes it’s just a small hiccup you can check yourself in a few minutes.
In this post, we’ll go over the most common things that can cause your heat pump’s outside unit to stop running, and what you can do about it.
#1 Check The Power Supply
This one sounds obvious, but you’d be surprised how often the issue comes down power issues. Heat pumps pull a lot of electricity, so if something cuts that flow, the whole outdoor unit shuts down.
The first place to look is your electrical panel. Flip the breaker for the heat pump off and back on, just to make sure it didn’t trip. If it keeps tripping, that’s a red flag, but more on that later.
Next, find the disconnect switch near the unit outside. Most systems have a small box mounted on the wall. Sometimes it’s a pull-out tab, other times it’s a flip switch. If that switch is off, the outdoor unit can’t run.
It may have been bumped, turned off during maintenance, or just got loose.
A quick reset there can bring your system back to life.
Also Read: Can A Thermostat Go Bad?
#2 Inspect The Thermostat
If the power’s good but the outside unit still isn’t running, it could be the thermostat.
The thermostat is basically the brain of your HVAC system, and if it’s on the fritz, your heat pump isn’t going to do its job.
Make sure the thermostat is set to the mode you actually want -“heat” in winter, “cool” in summer. Then check the temperature setting. If you set it at 72 but the room is already 72, the system might just be resting.
Another sneaky issue is batteries.
Some thermostats run on wall power, some on batteries, and some use both. Dying batteries can cause miscommunication between the thermostat and the outdoor unit.
If you haven’t changed them in a while, swap them out. Still nothing? Then it could be the thermostat itself acting up, which may call for a replacement.
#3 Look For A Faulty Contactor Or Capacitor
If the thermostat is working fine, then we’re getting into the technical stuff.
The contactor and capacitor are parts that help start and run the outside unit’s compressor and fan. If either one of these parts is faulty, your outside unit won’t be running.
A contactor is a type of electrical switch. When it goes bad, it might not send the right signals to turn the unit on. The capacitor, on the other hand, stores energy and gives the compressor and fan the “kick” they need to get going.
If the capacitor is busted, you might notice a humming sound without the unit actually starting up.
You can check these parts by inspecting the control panel of your unit (make sure the power is off before you do that).
If you see any signs of burning or corrosion, that’s a red flag, and you might need to replace these parts. Don’t worry, you can get them from most HVAC suppliers or online.
Unless you’re comfortable working with electrical components, this is usually the point where it’s smart to step back and let a pro handle it. High voltage and stored energy make capacitors tricky and even dangerous.
Also Read: Split AC Not Cooling But Fan Is Running?
#4 Check For Ice Or Blockages
Heat pumps are designed to sit outside in the elements, but that doesn’t mean they’re indestructible. Ice can build up on the coils in winter, especially if airflow is restricted or refrigerant levels are low.
A unit that’s frozen solid can’t breathe, and it may shut itself down as protection.
The other issue is debris. Leaves, sticks, dirt, even nests can clog up the system. A blocked fan or coil makes the outdoor unit struggle until it finally stops.
Walk around your heat pump and look for ice, frost, or obvious obstructions.
If it’s icy, turn the system off and let it thaw naturally.
Don’t chip at it with a tool since that can bend fins or break something delicate.
For debris, clear the area at least two feet around the unit so it has room to pull in air.
Keeping the space tidy goes a long way in avoiding future shutdowns.
#5 Listen For The Compressor
Sometimes the outdoor fan is running but the compressor is quiet. Other times, the whole thing is silent. Either way, your ears can give you clues.
If the fan spins but the compressor won’t start, it may point to low refrigerant, an overheated compressor, or electrical trouble inside the unit.
If both the fan and compressor are dead quiet, you could be dealing with a power supply issue or a total breakdown of one of those key parts like the capacitor.
The compressor is basically the heart of the heat pump, so if it’s not running, you’ll definitely feel it indoors.
Diagnosing the exact reason often requires tools that measure voltage or refrigerant pressure, which makes this another area where professionals can help.
Also Read: Why Is My A/C Running but Not Cooling the House?
#6 Check Safety Switches
Modern heat pumps are built with self-protection in mind.
If the system senses something dangerous (like too much pressure in the refrigerant lines or not enough) it will shut itself down.
These are called safety switches, and they’re designed to prevent bigger and more expensive damage.
The tricky part is that when a safety switch trips, the outdoor unit won’t give you much of a clue why. You might just see a silent box sitting there.
Sometimes the issue is temporary, like a power surge or short-term airflow problem. Other times, it’s pointing to something more serious, like a refrigerant leak or blocked coil.
If you’ve already checked power, thermostat, and blockages, but the system still won’t run, the safety switch could be the thing holding it back. Resetting or bypassing it yourself isn’t a good idea – you want the system to protect itself until the real cause is found.
When To Call A Pro
At this point, you’ve covered the easy stuff. If the outdoor unit still refuses to run, it’s time to bring in someone who knows these machines inside and out.
HVAC techs have the tools to test voltage, pressure, and internal components safely. They can spot worn-out capacitors, replace bad contactors, refill refrigerant, and even diagnose compressor problems that would otherwise be a guessing game.
Trying to push past the basic checks on your own can lead to bigger headaches, not to mention risks with high voltage and refrigerant exposure.
So if you’ve gone through the list and the unit is still silent, don’t sweat it, just call for service.
You’ll save yourself stress and probably money in the long run.
Bottom Line
If the outside unit of your heat pump isn’t running, don’t freak out just yet!
Take a few minutes to check the power supply, thermostat, contactor, and capacitor. Make sure there’s no ice or debris blocking the unit, and listen for any unusual sounds coming from the compressor.
Often, a small issue is the root cause, and with a little troubleshooting, you can get your system back up and running in no time.
If all else fails, don’t hesitate to call a pro. They’ll get to the bottom of the problem and save you from making things worse.
Either way, your home will be comfortable again, and that’s what really matters.