Oil Furnace or Boiler Not Working? 7 Safe Checks First

From the Alcus family · Alcus Fuel Oil & Sons, Amityville · Updated October 30, 2026

House getting cold? Before you call, these safe checks fix a surprising number of "no heat" problems. If you smell gas or your carbon monoxide alarm is going off, stop: get everyone outside and call 911.

7 safe checks

1. Thermostat. Is it set to HEAT and a few degrees above room temperature? Replace the batteries if the screen is blank.
2. Emergency switch. Most oil burners have a red-plate switch at the top of the basement stairs or near the boiler. Make sure it's ON — it often gets flipped by mistake.
3. Circuit breaker. Check the breaker or fuse for the boiler or furnace.
4. Oil level. Look at the tank gauge. If it says E, you're probably out — see ran out of oil. (How to read the gauge.)
5. Reset button — once. If the red reset button on the burner's control is popped up, press it one time. If the burner doesn't stay on, don't press it again. Call us.
6. Furnace filter (warm-air systems). A badly clogged filter can make a furnace shut itself off. Replace it if it's dirty.
7. Boiler water and zones (hot-water systems). If only some rooms are cold, a zone valve or circulator may be the issue — that's a service call, not a DIY job.

Stop and call right away if…

• You smell oil smoke, see soot, or hear a "puff-back" — turn the emergency switch off and call.
• There's oil on the floor around the tank or burner — see our oil leak steps.
• The burner trips again after one reset.
• Pipes are freezing — see frozen pipes.

Avoid the next one

Most no-heat calls we see come from a burner that hasn't been cleaned in a while, or a tank that ran dry. A yearly tune-up and automatic delivery prevent both. Service contract customers also get priority no-heat calls.

Questions