Heating help for Houston homeowners
No Heat in Houston? Likely Causes and Safe Checks
Learn why a furnace, heat pump, electric air handler, or mini-split may give no heat or weak heat and what is safe to check.
Written by William Bonilla
Reviewed by Sotero Bonilla, TDLR License TACLB23855E
Last updated
What should I do when my heat stops working?
A loss of heat may involve thermostat, airflow, ignition, heat-strip, or heat-pump faults. Check the thermostat, filter, open vents, mini-split settings, and observe a heat pump from outside. Do not check equipment if you smell gas or a carbon monoxide alarm sounds. A technician tests the heating sequence and airflow to confirm the cause.
No heat or weak heat can start at the thermostat, airflow, gas-furnace ignition, electric heat strips, or heat-pump equipment. Many of the same parts can fail partially before heat stops.
In a cold front, check people and pets. If you smell gas or a carbon monoxide alarm sounds, do not check equipment. Follow the emergency steps below.
What causes a furnace or heat pump to stop producing heat?
No heat can result from a failed run capacitor, clogged air filter, failed dual run capacitor, failed hot surface ignitor, or dirty flame sensor. The causes differ among furnaces, heat pumps, electric air handlers, and mini-splits. Testing the correct heating sequence, electrical operation, and airflow shows where the heat call fails.
These are possibilities, not a diagnosis. The order starts with common explanations, but the right answer depends on the equipment and what it does during testing.
Failed run capacitor
A weak capacitor can leave the outdoor unit humming while its fan or compressor cannot start.
Clogged air filter
A clogged filter restricts airflow, causing weak air, long cycles, higher energy use, or coil ice.
Failed dual run capacitor
One failed dual capacitor can stop both the outdoor fan and compressor or leave the unit humming.
Failed hot surface ignitor
A cracked or worn ignitor can let a gas furnace try to start without lighting its burners.
Dirty flame sensor
A coated flame sensor may shut the furnace down seconds after ignition because it cannot prove flame.
Burnt or stuck contactor
Heat or insects can damage this outdoor electrical switch, causing no start, chattering, or incorrect operation.
Dead or failing thermostat
Dead batteries or a failed thermostat can prevent the equipment from receiving a call to run.
Tripped breaker or blown disconnect fuse
A surge or overload can interrupt power, but a repeat trip signals a fault that needs testing.
Dirty mini-split filters or indoor coil
Dust on mini-split filters or the indoor coil can restrict airflow and reduce heating or cooling.
Failed condenser fan motor
A worn outdoor fan motor may stay still while the compressor hums, causing overheating and poor performance.
Electric heat strip or sequencer failure
A failed electric heat strip, relay, or sequencer can leave strong airflow with little heat.
Mini-split fan or control fault
A mini-split fan or control failure can stop airflow, make noise, or trip the circuit.
Failed blower motor
A failed indoor blower motor leaves little or no air at the vents even when other equipment runs.
Normal heat pump defrost cycle
Brief cooler air and outdoor steam can be normal when a heat pump melts frost and heating returns.
Duct leakage or undersized return
Leaky or undersized ducts can cause weak airflow, uneven rooms, humidity, and high energy use.
Mini-split remote or settings issue
The wrong remote mode, a met target, or an active timer can make a mini-split seem unresponsive.
Failed variable-speed blower motor
A failed variable-speed motor or control module can stop airflow or make it rise and fall oddly.
Failed inducer motor
A failed inducer cannot clear the flue, so the furnace safety sequence prevents ignition.
Failed furnace control board
A failed furnace board can stop ignition and airflow, cause erratic operation, or lock out the system.
Faulty gas valve
A failed gas valve can let the furnace complete its starting sequence without supplying fuel for heat.
Dirty blower wheel
Dust buildup on the blower wheel can leave airflow weak even after the filter is replaced.
Failed low-voltage transformer
A failed low-voltage transformer can blank the thermostat and stop controls even when main power remains.
System at the end of its service life
Older equipment with repeated failures, high energy use, or a major fault may warrant comparing repair and replacement.
Stuck heat pump reversing valve
A stuck reversing valve may make a heat pump deliver the opposite of the thermostat request.
Failed heat pump defrost control
A failed defrost control lets outdoor ice build and reduces heat-pump performance in cold weather.
What is safe to check yourself
- Set the thermostat to HEAT above room temperature. Replace accessible thermostat batteries if the screen is blank.
- Replace a clogged filter. Open supply vents and clear the large return grille.
- For a mini-split, confirm HEAT mode, a higher target, and no active timer.
- Observe a heat pump from outside. A brief pause, cooler air, and steam can be normal if heat returns. Do not touch the unit.
Keep every equipment panel closed. Do not touch wiring, pull an outdoor disconnect, or handle any internal part.
Stop and call right away if...
- If you smell gas or rotten eggs, do not troubleshoot or touch a switch. Leave with everyone and all pets, call the gas company and 911 from outside, then call us.
- If a carbon monoxide alarm sounds, take everyone and all pets outside into fresh air and call 911. Do not return until responders say it is safe.
- If you smell burning or hot electrical parts, turn the system off at the thermostat. Shut off its breaker only if safe. Leave and call 911 if there is smoke or sparking.
- If you see smoke or sparks, get everyone outside and call 911. Do not open the equipment or try to find the source.
What a technician will actually do
A technician follows the correct sequence: ignition and flame safety for gas, heat-strip controls for electric systems, or outdoor and defrost operation for heat pumps.
Airflow is checked before a major part is blamed. The technician then explains the confirmed fault.
Questions homeowners ask
- Why is my furnace running but not making heat?
- Possible causes include the ignitor, flame sensor, gas valve, airflow, or controls.
- What can I safely check for no heat?
- Check thermostat settings and batteries, the filter, open vents, mini-split settings, and a heat pump from outside.
- What if I smell gas when the heat will not start?
- Do not troubleshoot. Leave, call the gas company and 911 from outside, then call us.
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