Heat Pump Not Heating or Cooling: Troubleshooting & Fixes
A heat pump that won't heat or cool typically fails because of low refrigerant, a tripped breaker, a clogged filter, or a frozen outdoor unit. Basic checks like resetting power and cleaning filters cost nothing and solve 40% of these problems. More complex issues like refrigerant leaks or compressor failure require a licensed technician, with repair costs ranging from $300 to $2,500 depending on the part.
Step-by-Step Fix
- 1
Check power and thermostat settings
Verify the indoor and outdoor units have power by checking that breakers are switched on at the electrical panel. Confirm your thermostat is set to heat or cool mode (not off or fan-only) and that the temperature setting is higher than the current room temperature for heating, or lower for cooling.
- 2
Inspect and replace the air filter
Locate the return air filter in your furnace or air handler, typically a 1-inch or 4-inch thick pleated filter. Hold it up to light; if you cannot see through it, replace it with a new filter of the same size, which costs $10-$25 and takes 2 minutes.
- 3
Clear debris from the outdoor unit
Walk outside and examine the condenser (the fan-like unit). Remove leaves, twigs, grass, and dirt from the fins and coils using a soft brush or garden hose on low pressure. Ensure at least 2 feet of clearance around the unit so air can flow freely.
- 4
Check for ice buildup on the outdoor unit
If the outdoor unit is covered in ice or frost, switch the thermostat to off and allow 1-2 hours for it to thaw. If ice returns within a day, this signals a refrigerant leak or airflow problem that requires a technician.
- 5
Listen for compressor operation and check refrigerant lines
Turn the system to cooling mode and stand near the outdoor unit for 30 seconds; you should hear the fan running and a faint humming from the compressor inside. Visually inspect the copper refrigerant lines running between indoor and outdoor units for visible leaks, cracks, or damage.
- 6
Reset the system and observe startup
Switch the thermostat to off for 5 minutes, then turn it back on to heating or cooling mode. Listen and watch for the outdoor fan to start within 3-5 minutes; if nothing happens after 10 minutes, the system likely needs professional service.
⚠️ Safety Notes
- Do not attempt to add refrigerant yourself; it requires EPA certification and specialized tools, and overcharging damages the compressor. Only a licensed technician should handle refrigerant.
- Turn off power at the breaker before accessing electrical components or opening panels to avoid electric shock.
- Avoid touching the outdoor unit's copper refrigerant lines and condenser coils with bare hands; they can cause frostbite or cuts.
When to Call a Pro
Call a technician if the outdoor fan does not run after 10 minutes, if you see refrigerant leaking (oily residue on pipes), if the unit freezes over repeatedly, or if it runs but produces no hot or cold air after 30 minutes. These symptoms point to compressor, valve, or refrigerant issues that require specialized diagnostics and repair.
Frequently Asked Questions
- Why is my heat pump freezing up?
- A heat pump freezes when airflow is restricted (dirty filter or blocked return vents), the outdoor temperature is below 32°F without defrost mode kicking in, or refrigerant is low. Clear filters and vents first; if freezing persists, have a technician check the defrost cycle and refrigerant level.
- How do I know if my heat pump refrigerant is low?
- Signs of low refrigerant include the outdoor unit freezing over, weak airflow from vents, and the system running constantly without reaching the set temperature. Only a technician with specialized gauges can confirm low refrigerant and recharge the system for $300–$600.
- Can a clogged air filter stop my heat pump from working?
- Yes, a severely clogged filter blocks airflow and can cause the system to shut down automatically or freeze up. Replace the filter with one matching your system's size; a new filter costs $10–$25 and takes 2 minutes.
- What should I do if my heat pump won't turn on at all?
- First, check that the breaker is on and the thermostat is in heat or cool mode with the temperature set correctly. If power is on and the thermostat is set right but the unit still won't start, contact a technician to test the contactor or capacitor.
- How often should I service my heat pump?
- Schedule professional maintenance once per year, ideally before heating season starts, to clean coils, check refrigerant, and inspect electrical connections. Annual service costs $100–$200 and extends the unit's lifespan by 5+ years.
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