Heat pump not heating? How to tell defrost mode from a real fault, what aux and emergency heat mean, and typical heat pump repair costs in Irving, TX.
A heat pump that blows lukewarm air on a 30°F morning isn’t necessarily broken — and one that seems fine can be quietly running up a huge electric bill on backup heat. If your heat pump is not heating, the first job is telling normal winter behavior apart from a real fault. Here’s how we sort it out on heat pump repair calls in Irving and Coppell, where heat pumps are common in apartments, townhomes and all-electric houses.
The common causes, from most to least likely on a North Texas winter call:
Somewhat. A heat pump delivers air around 90–100°F — warm, but noticeably cooler than a gas furnace’s 120–140°F. Held against your hand, it can feel cool even when it’s heating properly. Measure at a supply register: air 20–30°F warmer than the room is normal operation.
During defrost, the system briefly reverses to melt frost off the outdoor coil. You may see steam rising from the outdoor unit, hear a whoosh as the valve shifts, and feel cooler air indoors for a few minutes. Defrost cycles typically last 2–10 minutes and repeat every 30–90 minutes in cold, damp weather. That’s healthy.
| Mode | What Runs | When It Should Be On |
|---|---|---|
| Heat | Heat pump only | Most of the winter |
| Aux heat (automatic) | Heat pump plus electric strips | Defrost, deep cold, or big setback recovery |
| Emergency heat (manual) | Electric strips only | Only when the outdoor unit has failed |
Electric strips cost two to three times as much to run as the heat pump itself. If “Aux” shows on your thermostat for hours on a 45°F day, something is wrong — usually low charge, a failed outdoor unit, or a thermostat wired with aux as the first stage of heat. That pattern often shows up first as a high electric bill.
Light frost on the outdoor coil is normal in cold, humid weather. A solid block of ice that doesn’t clear is not. The usual causes are a failed defrost board or sensor, low refrigerant, a dead outdoor fan motor, or water dripping onto the unit from a roof without gutters. Freezing rain can also coat a unit in ice from outside — switch to emergency heat until it thaws, and don’t chip at the coil.
Our hard freeze prep guide covers what to do before and during a Texas ice storm.
These are typical DFW ranges, not quotes. On a heat pump past 12–15 years old, a reversing valve or major leak often tips the decision toward replacement — and whether to stay with a heat pump or switch to gas is covered in heat pump vs gas furnace in North Texas.
We repair every major heat pump brand across Irving, including Las Colinas and Valley Ranch, and neighboring Coppell. See our heat pump services, or heating repair for gas and dual-fuel systems.
Call 214-900-2533. The office is open Monday through Friday 7–7 and Saturday 8–5, and emergency dispatch runs 24/7.
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Kenny founded Absolute Comfort Mechanical after more than 20 years in the Dallas–Fort Worth HVAC trade, because he was tired of watching homeowners get sold equipment they didn't need. He still runs diagnostics himself and reviews the technical advice published on this site.
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Absolute Comfort Mechanical HVAC — licensed, insured, family-owned, serving the Dallas–Fort Worth metroplex. Call 214-900-2533 for 24/7 AC repair, heating, cooling, and commercial refrigeration service.
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