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Heat Pump Running Nonstop in Cold Weather
Your heat pump has been running for hours without shutting off, the house feels okay but not warm, and you are wondering if something is broken. Long run times in cold weather are often normal. Constant running with a house that never reaches the thermostat setting is not. We repair heat pumps across Texas, Oklahoma and Louisiana, and here is how to tell the difference before you call.
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By the Trinity Air & Heat service team · reviewed by our working technicians
What Nonstop Running Actually Means
A heat pump moves heat instead of making it, so the colder it gets outside, the less heat there is to move. On a 30 degree morning your unit may run for an hour or more straight to hold 70 inside. That is the system working as designed, not a failure. The line to watch is temperature, not runtime. If the thermostat says 70, the house reads 70, and the air from the vents feels warm, you are fine. If the house is losing ground and the setting keeps slipping further away, something is wrong and it is worth a look before the next cold front.{
Cause One: Airflow and Filters
Start here because it is the cheapest and most common. A loaded filter chokes the blower, so the system moves less air, transfers less heat, and runs longer trying to catch up. Closed or blocked vents do the same thing. In a lot of 1990s subdivisions across the region the return duct was undersized from day one, so a dirty filter pushes an already tight system over the edge. Attic air handlers make it worse because leaky or crushed flex duct dumps warm air into an unconditioned attic. Change the filter, open every supply and return, and see if runtime improves over the next day.
Cause Two: The Outdoor Unit and Defrost
Heat pumps build frost on the outdoor coil in cold damp weather, and a defrost cycle is supposed to melt it off every so often. You may hear a whoosh and see steam. Normal. What is not normal is a solid sheet of ice covering the coil or the top of the unit for hours. That points to a failed defrost control, sensor or reversing valve, and it will run the unit nonstop while delivering almost nothing. Clear leaves, grass clippings and hail-bent debris from around the cabinet so air can get through. Do not chip ice off the coil or pour hot water on it.
Cause Three: Refrigerant Charge and Controls
If airflow is clean and the coil is not iced, the next likely families are low refrigerant charge, a struggling compressor, a stuck reversing valve or auxiliary heat that never engages. Low charge from a leak means the system can move only a fraction of the heat it should, so it runs constantly and the air from the vents feels cool. Thermostat wiring and configuration cause this too. A heat pump wired without a proper aux heat stage, or set to emergency heat by accident, will behave strangely. Refrigerant and high voltage work are ours to handle, not a homeowner project.
What Is Safe for You to Check, and What We Do Differently
Safe list: swap the filter, check thermostat batteries and confirm it is on Heat rather than Emergency Heat, look for a tripped breaker, clear debris around the outdoor unit, and walk the house confirming vents are open. That is where it stops. When we arrive we take supply and return temperatures to measure actual heat delivery, check static pressure to find the airflow restriction, put gauges on to read charge and superheat, test the defrost board and sensor, and verify the reversing valve shifts. If you smell gas near a dual fuel system, leave the house, call 911 or the gas utility, then call us.
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Heat Pump Running Nonstop in Cold Weather — common questions
Is it bad for a heat pump to run all day in winter?
Not by itself. Long runtimes are how heat pumps hold temperature in cold weather. The problem is running constantly while the house keeps getting colder or the vent air feels cool.
Why is my outdoor unit covered in ice?
Light frost is normal and defrost cycles clear it. Heavy ice that stays for hours usually means a failed defrost sensor, control board or reversing valve. Do not chip it off. Have it diagnosed.
Should I switch to emergency heat instead?
Only briefly, if the heat pump has clearly failed. Emergency heat runs electric strips that cost far more to operate. Use it to stay warm until we can look at the system, not as a fix.
How it works
- Step 1
Tell us the symptom
Call or fill in the quote form with what you hear, smell or feel. Warm air, short cycling, a breaker that keeps tripping. Details on your porch help us arrive with the right parts.
- Step 2
We diagnose on site
A technician checks the thermostat, airflow, the indoor coil and blower, then the outdoor unit and electrical side. You get a plain explanation of what failed and why it failed.
- Step 3
You approve the repair
We walk you through the fix and any parts involved before we start. Once you say go, we make the repair and confirm the system is holding temperature before we leave your driveway.
- A real person answers
- Open 7 days
- Written quote before work starts
Why homeowners call us
- Built for hard summersWe work on attic air handlers in July heat, undersized returns in older subdivisions, and condensers with hail-flattened fins. Those are everyday jobs across the region, so we know where these systems tend to give out first.
- Air conditioner repair and heating repairOne crew for both seasons. Air conditioning repair when the house won't cool, heater repair and furnace repair when the burners won't stay lit. Same technicians, same records, so nobody starts from scratch in November.
- We explain the failureYou hear which component failed and what it was doing to the rest of the system. If a repair is a short-term patch on an aging unit, we say so and let you decide the timing.
- Respect for the houseDrop cloths, shoe covers, and the attic hatch closed the way we found it. We keep the work area clean and we tell you honestly when a problem is airflow or ductwork rather than the equipment itself.
- All major brands, gas & electricOne independent crew for Carrier, Trane, Lennox, Goodman, Rheem and more.
- Straight answersIf a system is not worth repairing, we say so, often right on the phone.
About this guide
If the safe checks didn't fix it, the fault is real
Describe what you found and we'll take it from there. Booking takes about a minute.
- A real person answers
- Open 7 days
- Written quotes
- All major brands
- Gas & electric
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