First, which system heats your home?
Look at how the heat reaches the rooms. Vents in the floor or walls that blow warm air mean a forced-air system, either a gas or oil furnace or a heat pump with an air handler. Radiators or baseboard with water pipes mean a boiler. Thin metal baseboard on its own circuit with no pipes is electric resistance heat. Warm floors with no visible emitters usually mean radiant tubing fed by a boiler, or electric heating mats under the flooring.
A heat pump is the outdoor unit that looks like an air conditioner but also runs in winter. It moves heat from outdoor air into the house and often has electric backup strips, or a furnace, for the coldest days. Many homes have one system for the main floor and a different one for an addition, so a single cold room can be its own small mystery.
Once you know the system, the specific pages go deeper: furnace repair for forced-air gas furnaces and boiler repair for radiators, baseboard and radiant floors. This page covers the problems that cross over between systems.
What is usually wrong
| What you notice | Likely cause | Where to look first |
|---|---|---|
| No heat anywhere, thermostat screen blank | Dead batteries, tripped breaker or a blown low-voltage fuse | Thermostat and electrical panel |
| Thermostat calls for heat, nothing starts | Wiring fault, failed transformer or a locked-out furnace or boiler | Equipment error light |
| Heat pump blows cool air in winter | Defrost cycle, low refrigerant, a stuck reversing valve or failed backup heat | Outdoor unit and air handler |
| Outdoor heat pump coil caked in ice | Defrost control, sensor or airflow problem | Defrost board, fan |
| Some rooms cold, others too warm | Duct leaks, closed dampers, a failed zone valve or poor balancing | Ducts or zone controls |
| Radiators warm at the bottom, cold at the top | Air trapped in the radiator | Bleed valve |
| Electric baseboard dead in one room | Line-voltage thermostat or a tripped breaker | Wall thermostat |
| Heat runs constantly and the house never warms | Undersized equipment, big duct leak or a failing component | Full diagnosis |
A short list of checks solves a surprising share of no-heat calls before anyone arrives: fresh thermostat batteries, the thermostat set to HEAT and a few degrees above room temperature, the breaker for the furnace, air handler or boiler, the service switch near the equipment (often a light switch that someone flipped off by mistake), and a clean filter on forced-air systems.
Thermostat problems
Thermostats fail more often than people expect, and they are frequently blamed for problems they did not cause. Signs of a real thermostat fault include a blank or flickering screen with fresh batteries, a reading several degrees off from a separate thermometer, or equipment that starts when you jumper the wires at the furnace but not from the thermostat.
Smart thermostats add a common trap: many need a constant-power C wire, and without one they can drain, reboot or cycle the system oddly. Heat pump thermostats must also be set up for the right reversing valve setting and auxiliary heat staging; a wrong setting can make a heat pump cool in winter. A technician can check the wiring and settings in a few minutes.
Heat pumps in heat mode
Heat pump air feels cooler than furnace air, often in the 90s at the register rather than well above 100°F, so it can feel like it is not working when it is. On cold, damp days the outdoor coil frosts, and the system runs a defrost cycle for a few minutes, sometimes with steam rising from the unit and cool air inside. Both are normal.
Real problems look different: an outdoor unit that is a solid block of ice, a fan that will not spin, cool air for long stretches, or high electric bills from the backup strips doing all the work. Common causes are low refrigerant from a leak, a failed defrost board or sensor, a weak capacitor, a reversing valve stuck in cooling, or burned-out backup heat elements. Refrigerant work requires an EPA-certified technician.
Typical heating repair prices
| Repair | Typical range | Notes |
|---|---|---|
| Diagnostic visit | $90–$200 | Higher at night, weekends and holidays |
| Thermostat replacement and setup | $150–$450 | Smart models and new C-wire runs cost more |
| Capacitor or contactor (heat pump) | $150–$400 | Common, quick, often on the truck |
| Defrost control board or sensor | $250–$650 | Brand-specific parts |
| Backup heat strip or sequencer | $250–$700 | Size of the strip heater |
| Refrigerant leak search and recharge | $300–$1,500 | Leak location and refrigerant type |
| Zone valve or zone damper | $200–$600 | Boiler valve vs duct damper motor |
| Electric baseboard thermostat or heater | $150–$500 | Line-voltage wiring, heater length |
Major failures like a heat pump compressor, a reversing valve or a furnace heat exchanger usually cost far more and lead to a repair-or-replace conversation. Ask for the price of each option in writing.
Uneven heat and cold rooms
When the system runs fine but some rooms lag, the cause is usually distribution, not the furnace, boiler or heat pump. In forced-air homes, look for closed or blocked registers, crushed or disconnected ducts in an attic or crawlspace, and dampers left in summer positions. In boiler homes, look for air in a loop, a zone valve that sticks, or baseboard fins packed with dust and pet hair.
Rooms over garages, sunrooms and additions are often cold because they were added without enough heat delivery. Sometimes a duct fix or a balancing adjustment is enough; other times a ductless mini-split for that room is the cleaner answer.
Repair or replace
Rough life spans: gas furnaces about 15 to 20 years, heat pumps about 10 to 15 years, boilers anywhere from 15 to 30 years depending on type, and electric baseboard much longer. When the equipment is near the end of that range and the repair is a compressor, a heat exchanger or a major motor, it is reasonable to price a replacement before committing. For boilers specifically, see boiler replacement.
Safety when the heat goes out
If you smell gas, get everyone out of the house, leave doors open behind you, and reach the gas utility or 911 from a neighbor's house or the street before you call a heating company.
Never heat the house with a gas oven or range, and never run a generator, grill or camp heater indoors or in an attached garage. Those are leading causes of carbon monoxide poisoning in winter. If you use a portable electric space heater, keep it three feet from anything that can burn, plug it straight into a wall outlet and turn it off when you leave the room.
In a hard freeze, open cabinet doors under sinks on outside walls and let faucets drip to protect the plumbing until heat is back. A boiler home is at extra risk because the heating pipes themselves can freeze.
Seasonal maintenance
- Fall tune-up for the furnace, boiler or heat pump before heating season starts.
- Filters on forced-air systems checked monthly during heavy use.
- Outdoor heat pump unit kept clear of snowdrifts, leaves and roof runoff dripping onto it.
- Radiators bled and baseboard fins vacuumed at the start of each winter.
- Thermostat batteries replaced yearly, and CO alarms tested monthly.
What to ask the heating contractor
- Are you licensed and insured for HVAC work here, and EPA certified for refrigerant?
- Do you work on my type of system (furnace, boiler, heat pump) and my brand?
- What is the diagnostic fee, and is it credited toward the repair?
- Can you give me the repair price and a replacement price if the system is older?
- What warranty do you offer on parts and labor?
Questions people ask
How much does heating repair usually cost?
Most repairs fall between $150 and $700 including the visit. Thermostats, capacitors and sensors sit at the low end; refrigerant leaks and backup heat repairs run higher.
Why is my heat pump blowing cold air?
It may be in a normal defrost cycle, which lasts a few minutes. If cool air continues for a long time, the cause may be low refrigerant, a stuck reversing valve or failed backup heat, and a technician should check it.
My thermostat says heat is on but nothing happens. What should I check?
Swap the thermostat batteries, confirm the breaker is on, make sure the unit's power switch was not flipped off, and look for a blinking error light on the furnace or boiler. If those are fine, the problem is likely wiring, a control board or a lockout.
Why are some rooms colder than others?
Usually a distribution issue: leaky or crushed ducts, closed registers, air in a hydronic loop or a stuck zone valve. Additions and rooms over garages are common trouble spots.
Is it safe to use a space heater while I wait for repair?
An electric space heater is fine if it has tip-over protection, sits three feet from anything that can burn and plugs directly into a wall outlet. Never use a gas oven or outdoor heater indoors.
Can someone come out tonight for no heat?
The line is open 24/7, and most areas have heating techs on emergency duty through the cold months. If there are young children, older adults or a risk of frozen pipes, say so on the call.
Who should I call for heating repair, a plumber or an HVAC company?
For furnaces and heat pumps, an HVAC company. For boilers, look for a heating contractor who services hydronic or steam systems; some plumbing companies do this work too.