05·RB-HEAT
Runbook — No heat
The house is cold. Four of the five likely causes are things you can check yourself in under ten minutes, and none of them need tools.
956 N Noble Loop · Showing Edition · Rev A · Aug 2026
Start at the thermostat, not at the furnace. The Ecobee is the brain of the heating system, and a surprising share of “the furnace is broken” calls end at the wall in the hallway — a mode setting, a schedule, or a thermostat that lost power because the furnace did. Work outward from there.
If you smell gas at any point — stop
Do not switch anything on or off, do not use a light switch or a phone indoors. Leave the house, then call 911 or NW Natural’s 24-hour emergency line, 800-882-3377, from outside. The same applies to a carbon monoxide alarm: get everyone out, then call 911. Heating equipment burns fuel, and this is the one failure mode that is genuinely dangerous rather than merely uncomfortable.
First, check — in this order
- Wake the Ecobee and look at the screen. Is it lit at all? A completely dark thermostat is a power problem, not a thermostat problem — skip to step 4.
- Check the mode and the target. The mode must be Heat or Auto, and the target temperature must be above the current room temperature. In Auto, a target that sits between the heating and cooling setpoints means the system correctly does nothing. This is the single most common cause and it costs nothing to rule out.
- Check for a hold, an Away, or a Vacation setting. If someone set a vacation schedule or the geofencing put the house in Away, the Ecobee is heating to a lower target on purpose. Cancel the hold or the vacation event in the app or on the screen.
- Check the furnace power. There is a switch on or beside the furnace that looks exactly like an ordinary light switch — someone tidying the utility area switches it off surprisingly often. It must be ON. If it is, check the furnace’s breaker at the panel: see breaker trips. The Ecobee is powered from the heating system, so no power at the furnace means a blank thermostat too.
- Check the furnace door. Most furnaces have a safety switch that cuts power when the front panel is off or not seated. If someone changed a filter recently, reseat the panel firmly.
- Check the filter. A clogged filter starves the furnace of airflow and it shuts itself down on a high-limit switch — usually after running briefly and blowing lukewarm air. If the filter is grey and matted, replace it and try again. Filter size to be measured and recorded at the walkthrough — see the Ecobee page.
- Check that gas is reaching the house. Light a burner on the BlueStar range. If the range lights, gas service is fine and the problem is the furnace. If nothing gas-fired in the house works, call NW Natural, 800-422-4012 (or 800-882-3377 if you suspect a leak).
- Check the condensate drain. High-efficiency furnaces produce water and drain it through a small tube, often to a pump or a floor drain. If that drain blocks or the pump fails, a float switch shuts the furnace down — a classic wet-climate fault that looks exactly like a dead furnace. Look for standing water in or under the unit.
- Give it one clean restart. Switch the furnace off at its switch, wait thirty seconds, switch it back on, then set the Ecobee a few degrees above room temperature. Many furnaces lock out after three failed ignition attempts and a power cycle clears the lockout. If it starts and runs, watch it through a full cycle before declaring victory.
- Check the vents. Supply registers open, return-air grille unblocked by furniture or a rug. A house that heats unevenly rather than not at all is usually an airflow problem, not a furnace fault.
Symptom → cause → fix
| Symptom | Likely cause | What to do |
|---|---|---|
| Thermostat screen is blank | The heating system lost power — the Ecobee runs off it. | Check the furnace switch, then the furnace breaker. The thermostat is almost never the failed part. |
| Thermostat is on and calling for heat, nothing happens | Furnace power, a lockout, a door switch, or a control fault. | Work steps 4–9 above. If the furnace does not even attempt to start — no click, no fan, no ignition noise — it is a power or control problem. |
| Furnace starts, runs briefly, shuts off, repeats | Short-cycling: usually a dirty filter, a blocked return, or overheating on the high-limit switch. | Replace the filter and clear the returns. If it continues with a clean filter, call an HVAC technician — repeated overheating is hard on the heat exchanger. |
| Blower runs but the air is cold | No ignition, no gas, or a failed igniter/flame sensor. | Confirm gas elsewhere in the house, try one power-cycle to clear a lockout. Repeated failure to ignite is a service call. |
| Furnace tries three times then goes quiet | Ignition lockout — the control board gave up on purpose. | One power cycle at the furnace switch resets it. If it locks out again, stop and call an HVAC technician; the fault is real. |
| Some rooms warm, some cold | Airflow: closed registers, blocked returns, filter, or duct balance. Or sensor placement. | Open registers, clear returns, replace the filter. If the Ecobee has remote room sensors, check which rooms they are in and how they are participating — see the Ecobee page. |
| Ecobee shows offline in the app but the house is warm | It lost WiFi. Heating is unaffected. | Not urgent. See internet down, then re-run WiFi setup on the thermostat. |
| No heat and the power is out | Nothing — the Powerwalls should be running the furnace. | See power outage. If the batteries have gone to standby, heat stops with everything else. |
| Water around the furnace | Blocked condensate drain or a failed condensate pump. | Clear or have the drain cleared; the furnace will not run until the float switch is satisfied. Also see water leak. |
| Burning smell on the first cold day of the year | Dust on the heat exchanger. | Normal, and it clears within an hour. A persistent burning or electrical smell is not normal — shut it down and call a technician. |
While you wait for heat
Keep the house above freezing to protect the plumbing: if it will be many hours, open cabinet doors under sinks on exterior walls, and let a faucet drip. Space heaters work but are among the heaviest loads in a house — one per circuit, never on an extension cord, and remember they will drain the Powerwalls fast if the grid is also down. The gas range is not a heater; never use it to warm a room.
Owner's edition
Full details in the owner's edition — serial numbers, configuration and identity details continue in the complete manual, handed to the buyer at closing.
Stop and call a pro when…
- You smell gas — leave the house, then 911 or NW Natural 800-882-3377 (24-hour). Never troubleshoot through a gas smell.
- A carbon monoxide alarm sounds — everyone out, then 911. Do not re-enter to investigate. CO is the reason furnace faults are not a DIY category.
- The furnace locks out repeatedly, short-cycles with a clean filter, or will not ignite — an HVAC technician. Ask them to check the heat exchanger, the flame sensor, and the condensate path while they are there.
- There is soot, scorching, or a cracked-looking heat exchanger — shut the system off at its switch and call an HVAC technician before running it again.
- There is no gas anywhere in the house — NW Natural 800-422-4012.
- The furnace has no power and its breaker will not hold — a licensed electrician, not an HVAC technician.
Related pages
- Ecobee thermostat — everyday operation, schedules, sensors, filter reminders, and its own troubleshooting list. This runbook is the emergency path; that page is the reference.
- Breaker trips — for the furnace circuit.
- Power outage — heating runs on the Powerwalls, and it is a meaningful load.
- Going on vacation — what to set the heat to when the house is empty in winter.
- ecobee — Support home
Official guides for every current model, including reset and WiFi setup. - NW Natural — Contact & 24-hour gas emergency line
Source for the emergency line 800-882-3377 and customer service 800-422-4012. - NW Natural — What to do if you smell natural gas
The official leave-then-call procedure. Worth reading once, before you need it. - Furnace / air handler manufacturer documentation
to add once the make and model are captured at the walkthrough — the manual, the parts list, and the filter specification will be archived here.