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Furnace not heating or locked out.

A licensed heating technician should do all gas, oil, burner and energized work past the thermostat and power switch.

Customers put it like this

  • The furnace won't come on
  • It tries to light then shuts off
  • It's only blowing cold air
  • The oil burner keeps locking out
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Stop first if

  • You smell gasLeave the building now. From outside, call emergency services or the gas utility.
  • A CO alarm soundsGet everyone into fresh air. Call emergency services from outside.
  • After resets, an oil burner chamber holds pooled oil or vapor, or runs very hotDo not press reset. Keep the burner off and call a licensed oil burner technician.
  • Water is on wiring or controlsKeep clear of it. A qualified person kills power at the disconnect while standing somewhere dry. Otherwise call a licensed electrician.
01

Ask on the call

6

Homeowner? These are the questions a good technician will ask you. Having the answers ready makes the first visit count.

  1. Is it gas or oil?
  2. What happens when the thermostat calls for heat?
  3. Does it show a code or blinking light, and can you read it before any reset?
  4. How many times has anyone pressed reset?
  5. Have you checked the thermostat, power switch and oil level?
  6. Does the furnace or its drain sit somewhere cold, like a garage, attic or crawl space?
02

Bring

5
  • Digital manometer
  • Meter with a microamp range
  • Combustion test instruments
  • Draft gauge
  • Flashlight
03

Check on site

6
  1. Record fuel, ignition type and venting. Pull stored faults while power and the door are still untouched.
  2. Look through the sight glass during a heat call. Mark where the start-up stops.
  3. On oil, ask about resets and look for pooled oil before any restart.
  4. A licensed tech reads what that safety device senses, such as draft, gas pressure or flame signal.
  5. On a condensing unit, check the trap, drain and vent end for ice or blockage.
  6. Replace a part only if what it watches reads adequate and it still does not respond. Then run full cycles.
04

Keep on the record

5
  • Stored fault codes
  • The step where the sequence stopped
  • Readings taken at that step
  • Nameplate photo
  • Oil tank level, on oil systems

General guidance for a qualified person, not a finding about any home. The person on site decides.