November 24, 2025
Lakewood, CO Heat Pump Not Cooling? 5 Common HVAC Fixes
Estimated Read Time: 11 minutes
If your heat pump not cooling your home is the problem today, you are not alone. When outdoor temps rise, small issues can snowball into warm rooms, high bills, and nonstop runtime. The good news is most cooling failures trace to a handful of fixable causes. Below are the top five reasons and the exact steps you can take before calling a pro. If you need help today in the Denver area, we offer same-day and 24/7 service.
1) Thermostat or Mode Is Set Incorrectly
A heat pump must be in Cool mode with the fan set to Auto for consistent comfort. If it is in Heat, Emergency Heat, or Fan On, you will feel warm or room-temperature air. Start by setting the thermostat to Cool, lowering the setpoint 3 to 5 degrees below room temperature, and waiting 5 minutes for a cooling call to engage.
Quick checks you can do:
- Confirm the system schedule is not overriding your changes. Temporarily use Hold or disable the schedule.
- Ensure Eco or Away modes are off if you are home.
- Replace thermostat batteries if the screen is dim or unresponsive.
- Verify the breaker labeled Air Handler and Heat Pump is on. A tripped outdoor breaker means the indoor fan may blow but no cooling will occur.
Smart thermostats sometimes misidentify heat pump reversing valves. In settings, confirm the O/B reversing valve assignment matches your system. A wrong setting can keep the valve in heat when you want cool. If you recently changed thermostats, this is a common culprit.
Two hard facts that matter here: many manufacturers require correct thermostat configuration to keep warranty protection, and professional installation is often required to maintain warranty coverage. If you are unsure about wiring or O/B settings, schedule a quick diagnostic to avoid damage.
2) Restricted Airflow From a Dirty Filter or Blocked Outdoor Unit
Insufficient airflow starves your system. Indoors, a clogged filter or closed supply registers can reduce cooling capacity and cause the coil to ice. Outdoors, debris on the condenser coil keeps heat trapped in the refrigerant so your home never cools down.
Do this first:
- Replace your air filter. In cooling season, check monthly. A clean filter can recover lost capacity quickly.
- Open at least 80 percent of supply registers. Do not close more than a few rooms or you risk freezing the coil.
- Inspect the outdoor unit. In the Denver area, cottonwood fluff and dust can mat the coil in late spring. Gently hose from the inside out with the power off.
- Keep 2 feet of clearance around the outdoor unit. Move covers, yard tools, and vegetation.
At Colorado’s elevation, thinner air reduces heat transfer. A mildly dirty coil has a bigger impact here than at sea level. Keeping that coil clean is not optional for peak cooling.
If the indoor coil has visible frost or ice, turn the system Off and set the fan to On for 60 to 90 minutes to thaw it. Do not chip ice. After thawing, return the thermostat to Cool and monitor. If ice returns, you likely have a deeper airflow or refrigerant issue.
3) Low Refrigerant or a Refrigerant Leak
Your heat pump cools by moving heat, not making it. Low refrigerant means the system cannot absorb and release heat efficiently. The symptoms are longer runtimes, warm supply air, ice on the indoor coil, and sometimes a hissing sound near lines or the air handler.
Important notes:
- Refrigerant is not a fuel that gets used up. If it is low, there is a leak.
- Topping off without a leak repair is a short-term bandage and often violates best practice.
- Modern air-source heat pumps can post high efficiency ratings, with some models reaching about 20 SEER and 13 HSPF in heating mode, but only when charge is correct.
What a pro will do:
- Perform electronic and soap-bubble leak detection on coils, fittings, and line sets.
- Recover and weigh out remaining refrigerant, repair leaks, then evacuate to deep vacuum.
- Weigh in factory-specified charge and verify superheat and subcooling match manufacturer targets.
Because many manufacturers require professional service to maintain warranty coverage, DIY charging is risky. If you suspect a leak, shut the system down to protect the compressor and schedule service.
4) Frozen or Dirty Indoor Coil and Blower Problems
If your supply air is weak or warm, the indoor coil may be iced over or caked with dust. A weak blower motor or dirty blower wheel also chokes airflow. Both conditions lead to poor cooling, high energy use, and water around the air handler when the ice melts.
What you can do safely:
- Check the condensate drain and pan. A clogged line can trip float switches and stop cooling.
- Look for ice on the refrigerant lines or coil door. If present, turn cooling Off and fan On to thaw.
- Replace the filter and remove visible obstructions near returns.
Professional fixes may include cleaning the evaporator coil, balancing airflow, replacing a failing capacitor or blower motor, and verifying static pressure across the system. In multi-level Denver homes with long duct runs, undersized returns are common. Adding return capacity can restore cooling and reduce noise.
If your system has a variable-speed blower, incorrect dip switch or board settings can force low airflow in Cool mode. Technicians will match the airflow to your tonnage and ductwork so the coil does not re-ice.
5) Reversing Valve, Contactor, or Capacitor Failure
The reversing valve directs refrigerant flow to switch between heating and cooling. If it sticks or the solenoid fails, the unit may stay in heat or neutral and deliver no cooling. Likewise, a pitted contactor or weak capacitor can prevent the outdoor fan or compressor from starting.
Common signs:
- Outdoor fan runs, but compressor does not start.
- Loud humming at startup followed by a click and silence.
- Unit cools briefly, then stops, then repeats.
These are not DIY repairs. A certified technician will test coil voltage, measure capacitance, and verify control board signals. Replacing a contactor or capacitor is straightforward, but reversing valve issues require refrigerant recovery and brazing.
When this happens repeatedly, it is smart to inspect the entire electrical system, tighten connections, and confirm proper charge so components are not stressed by hard starts.
Bonus: Ductless and Geothermal Heat Pumps Have Unique Cooling Issues
Ductless mini-splits can lose cooling if filters behind the grille get dusty or if the outdoor micro-channel coil is clogged. Make sure the unit is not set to Dry or Auto with a high setpoint. Clean the washable filters monthly during peak cooling.
Geothermal systems rarely lose capacity unless there is an airlock, pump failure, or closed loop flow issue. If loop pressure is low or you hear gurgling, shut the system off and call for service. A trained tech will purge the loop, check pumps, and verify entering water temperature.
When to DIY, When to Call a Pro
Try these steps first:
- Set thermostat to Cool, 3 to 5 degrees below room temp, Fan Auto.
- Replace the air filter and open registers.
- Rinse the outdoor coil from inside out with power off and clear 2 feet around it.
- Check breakers and condensate drain safety switches.
Call a professional if:
- You see ice on lines or the coil.
- The outdoor unit hums but does not start.
- Supply air stays warm after basic checks.
- You suspect a refrigerant leak.
Our team offers 24/7 service and a rapid response commitment, with a 4-hour response window on many calls. We service Carrier, Goodman, Mitsubishi, Rheem, Trane, American Standard, and can install replacements that match your home and budget. Financing is available to spread out upgrades.
Prevent Cooling Problems Before They Start
Regular maintenance keeps performance high and catches small failures early. In Denver’s climate, a spring tune-up is essential. Our membership options make it easy.
What to expect from quality maintenance:
- Deep clean of indoor and outdoor coils, not just a rinse.
- Electrical testing of capacitors, contactors, compressor amps, and blower.
- Refrigerant performance check with superheat and subcooling.
- Thermostat calibration and mode verification.
- Condensate drain flush and safety switch test.
Our Green Club Membership starts at about $29.95 per month and includes routine service, 10 percent off HVAC repairs, and credits that apply to future repairs. Many homeowners recover their fee in one visit when a failing capacitor, dirty coil, or clogged drain is found early.
If your current system is old or undersized, we can right-size a new air-source or ductless system. Air-source heat pump installations often range from about $3,500 to $7,500, while ground-source systems can range higher. We will walk you through options and leave your home spotless after install.
Local Tips for Denver Metro Homeowners
Our dry air helps evaporate moisture, but high elevation reduces air density, which hurts heat rejection outdoors. That means clean coils matter more here. Cottonwood season can blanket outdoor fins in days. Rinse coils gently during peak fluff weeks.
Hail is common on the Front Range. Consider a factory hail guard for your outdoor unit. Keep landscaping trimmed to maintain airflow. For older homes in Denver, Thornton, and Lakewood with limited return air, adding return grilles can dramatically improve cooling comfort on the second floor.
What Homeowners Are Saying
"Alex H. did an exceptional job performing seasonal maintenance on our 2 furnaces and AC unit. Additionally, he was the only technician in 3 years able to clear an error code from our unit, enabling us to engage our heat pump. We highly commend his friendly and effective service." –Alex H., Denver
"I had a technician come to my house after hours, Myron, who was the most pleasant and knowledgeable person I have encountered in a while. He was able to resolve the reason my heat wasn’t working quickly and with a smile." –Myron M., Aurora
"Isaac was absolutely amazing. He had an amazing attitude and work ethic. He was determined to get our heat working and did not stop until it was fixed." –Isaac I., Lakewood
Frequently Asked Questions
Why is my heat pump running but not cooling?
Often the thermostat is on the wrong mode, the filter is clogged, or the outdoor coil is dirty. If airflow is fine, low refrigerant or a failed capacitor can stop cooling. Try basic checks, then call a pro for testing.
Should I turn off my heat pump if I see ice?
Yes. Turn cooling Off and the fan On to thaw the coil for 60 to 90 minutes. Do not chip ice. If ice returns after restart, you likely have airflow or refrigerant issues that need professional service.
How often should I change my filter in summer?
Check monthly and replace every 1 to 3 months. Homes with pets, construction dust, or wildfire smoke may need more frequent changes to maintain airflow and cooling.
Do heat pumps cool well in Denver’s climate?
Yes. Modern systems cool efficiently during our dry summers. Keep the outdoor coil clean during cottonwood season and ensure ductwork provides adequate return air for multi-level homes.
When should I repair versus replace?
If the system is over 12 years old, needs major components, or is undersized, consider replacement. A new, well-sized unit with up to about 20 SEER can cut bills and improve comfort.
Conclusion
A heat pump not cooling usually comes down to five causes: wrong settings, airflow restrictions, low refrigerant, frozen or dirty coils, or failed electrical parts. Quick homeowner checks can bring relief fast. For stubborn issues, expert diagnostics protect your warranty and your time. Denver’s elevation and cottonwood season make clean coils and proper airflow critical to comfort.
Schedule Cooling Help Now
Get same-day service from certified techs who follow manufacturer guidelines and protect your warranty. Call Fix-it 24/7 at (720) 734-7243 or schedule at https://fixmyhome.com/. Ask about our Green Club Membership starting at about $29.95 per month for routine tune-ups and 10 percent off repairs. We serve Denver, Aurora, Lakewood, Thornton, Arvada, Boulder, Westminster, Centennial, Lafayette, and Longmont.
About Fix-it 24/7 Plumbing, Heating, Air & Electric
Family owned and trusted across the Denver Metro, Fix-it 24/7 delivers expert HVAC service with EPA and NATE-certified technicians, A+ BBB rating, and thousands of 5-star reviews. We offer honest flat-rate pricing, 24/7 emergency response, and a 100% satisfaction guarantee. Financing is available through partners like GoodLeap, Wells Fargo, and GreenSky. We service leading brands and follow manufacturer guidelines to protect your warranty.