A Comfortmaker heater that will not come on in Sunnyvale, Santa Clara or Cupertino is usually a furnace stuck at one step of its start-up, and a heater technician’s first job is to find that step. Nights here get cold enough that furnaces and heat pumps run from November to March, so most Comfortmaker calls arrive in that window. We repair and maintain Comfortmaker gas furnaces, heat pumps, air handlers and central air conditioners. Comfortmaker is a Carrier Global brand, related to Carrier.
Comfortmaker heater not working: what the technician looks at
| Symptom | First check | Often turns out to be |
|---|---|---|
| Thermostat calls for heat, nothing happens | The switch beside the furnace, the breaker, the blower door | A switch left off, a door not seated on its safety switch, a blown control fuse |
| Lights, then shuts off within seconds, then tries again | Flame sensor | A coated sensor that needs cleaning or replacing |
| Runs a few minutes, burners go out, fan keeps blowing | Filter and return air | Overheating that trips the high-limit switch |
| Cold air from the vents in heat mode | Igniter and gas supply, or the outdoor unit on a heat pump | A cracked igniter, a gas valve fault, or a normal defrost cycle |
| A bang or boom when the burners light | Burners and ignition timing | Dirty burners delaying ignition |
| Water around a high-efficiency furnace | Condensate trap and drain line | A clogged trap or a disconnected drain hose |
The board’s status light often blinks a code, and the key to it is printed on the inside of the furnace door. Write the code down before you switch anything off, because on many boards cutting the power clears it. Our furnace repair page explains the repairs in more depth.
What a heater maintenance visit includes
A yearly tune-up catches most of the faults above before the first cold night. On a Comfortmaker furnace it covers:
- Filter replaced or checked, and return air paths cleared
- Flame sensor cleaned, igniter inspected
- Burner flame checked for a steady, even pattern
- Heat exchanger inspected for cracks or rust
- Vent pipe and draft checked; condensate trap cleaned on high-efficiency models
- Limit and rollout safety switches tested
- Blower wheel, motor and capacitor checked
- A carbon monoxide check around the furnace
- Thermostat tested through a full heating cycle
Plans and scheduling are on maintenance plans, with local pages for Sunnyvale furnace maintenance and Cupertino furnace maintenance.
Carbon monoxide: when to stop using the heater
Every home with a gas furnace needs working carbon monoxide alarms. If one sounds, get everyone outside and call 911 from there. If you smell gas, leave without flipping switches and call the gas company from outside. Soot around the furnace, a flame that is yellow and lazy instead of blue, or headaches that ease when you leave the house are reasons to shut the furnace off and call for an inspection. More in our carbon monoxide safety guide.
Comfortmaker heat pumps and air handlers
A heat pump heats differently from a furnace. The air from the vents feels warm rather than hot, and in cold weather the outdoor unit pauses now and then to melt frost off its coil, sometimes with a cloud of steam. Both are normal. A unit that stays iced, runs on backup heat all day or blows cool air for long stretches needs a look at the defrost controls, the reversing valve or the refrigerant. See heat pump repair.
Comfortmaker AC repair
The summer side follows its own order: thermostat demand, airflow, the outdoor fan, the capacitor and contactor, coil condition, and only then refrigerant and compressor readings. Many no-cooling calls end at an electrical part. Our AC repair page covers the rest.
Parts, warranty and urgent calls
Igniters, flame sensors, capacitors and contactors are standard parts, often replaced on the first visit; control boards and blower motors are matched to the model and may need to be ordered. Manufacturer coverage depends on the model and the install date. Our repairs are backed by a warranty covering both parts and labor.
No heat on a cold night or no cooling in a heat spell counts as urgent. Same-day service is available, urgent calls get the earliest opening, and our phones are staffed 24/7. The heating page covers every heating service we offer.