What To Do If Your Furnace Won't Start

Posted on October 31 2018

(Cue the scary music) It’s cold and your furnace won’t start. 

Actually, troubleshooting a furnace that uses heating oil and won’t start isn’t as scary as it sounds. That’s because there’s only a few things that the average person could (or should) try and do to remedy the situation.

Now, there might be times when your furnace isn’t running as well as you think it should and needs service. This isn’t about making a furnace run better – this is about what you should check out when your furnace just won’t run.

With any luck, one of these common “fixes” will do the trick and save you the time, money and potential embarrassment of having an oil company service tech come to your house just to flip a switch or install a new battery.

Here’s a short list of the most common reasons why your heating oil furnace won’t start up.

  1. The home’s thermostat is off or set incorrectly

  2. There’s no electricity reaching the home

  3. The Emergency Burner Shut Off switch was engaged

  4. There’s no heating oil in the tank 

Truth is, as important as it is to keeping your home comfy and warm, a furnace is actually a pretty simple machine.

Fuel (Heating Oil) + Spark = Flame and Heat

A furnace, sometimes called a ‘boiler’, is basically just a big torch that’s surrounded by a fireproof box.

The torch inside the furnace is used to either heat up a bunch of water, air or both. During the heating season, the amount of hot water or hot air it makes is controlled by a thermostat (or two, three) located in another room of the house.

When the thermostat gets cold, it tells the furnace to make some heat. When the thermostat warms up, it tells the furnace to shut off.

And that, is all there really is to it. More or less.

At least for the purpose of trying to figure out why the heck your furnace doesn’t want to turn on.

So, when it’s starting to get chilly outside and you want your furnace to start bringing the heat here’s some of the simple stuff to check before you go calling for help.

Check the thermostat 

These little buggers are really the brains of the whole home heating operation. Most everyone by now should have a thermostat that can be set digitally.

The newer thermostats allow people to set them up so that the heat comes on and off at different times, on different days.

Because they got ‘smarts’ (and unlike those old, round, rotary dial ones you used to see in your Grampy’s house) these thermostats do require batteries. If your furnace ain’t turning on – and it’s plenty cold in your house – make sure your thermostat batteries are still good.

Oh yeah, while you’re at it, make sure your thermostat is switched to the ‘Heat’ setting too. That lets the thermostat know what temperature it needs to be measuring in the room.

If the batteries are good and unit is turned on to the ‘Heat’ position, look at what the temperature is set to. Like any piece of technology, it only knows what you tell it.

If you – or someone else – has set the thermostat to come on once the room temperature falls to 55°(F), it’ll do just that. If the room temp is 60°(F) and you’re already cold, grab a sweater or reset the thermostat – cuz it won’t  come on until it’s 55° in the room - no matter what insults you hurl at it.

Check the electricity

OK, so now you might be thinkin’ “Hey? My furnace runs on heating oil, what do I need electricity for?”

The answer is that your heating oil-burning furnace still needs an electric spark to ignite the flame inside and get things cookin’.

It also needs electricity to power the blower/fan or pump that’s used to move the hot air or hot water from the furnace to other parts of the house.

Bottom line, if you got no juice, you’re getting no heat from your furnace until you do.

Check the Emergency Shut Off Switch

It happens. By law, every residence is required to have an Emergency Shut Off Switch that allows first responders, oil burner service technicians and others to be able to shut the furnace off. 

These switches look like regular light switches, but typically have a bright red faceplate and are in places that seem pretty inconvenient to get to – they are, and that’s by design.

Installing these switches in odd locations, for example, high on a wall in the middle of a flight of stairs coming up from the basement, is supposed to make it more difficult for the switches to be turned off accidently.

Still, it can happen. All it takes is for someone to brush by it while moving a mattress upstairs – or for your energetic 10 year old to “accidently” nail it with a soccer ball, and the furnace will stay quieter than a mouse, until someone goes and turns the switch back on again.

Check the heating oil tank

One last possibility of why your furnace won’t turn on is that you are out of heating oil.

If you’ve got power and you’re sure that the system is turned on, the next thing to check is whether or not you have heating oil in the tank.

The most common heating oil tank measures 275 gallons (although it only safely holds around 240 gallons). On the top of the tank, there’s usually a gauge (looks like a clear tube with lines on it) to indicate how much fuel is inside the tank.

A tank that shows ½ full will have approximately 120 gallons left inside. ¼ tank is about 60 gallons. If the indicator is below 18 or isn’t visible at all, the tank may be out of oil and needs to be refilled.  We recommend that customers order at ¼ of a tank.

If your furnace still doesn’t start

Then we recommend going to Googling HVAC companies near me, finding a couple with the best reviews and giving them a call.  They’ll be able to come out and get you going.  If you’re out of heating oil, go to heatable.com or our smartphone app and place an order ASAP.

For more troubleshooting tips, check out Heating Oil Safety and Troubleshooting Tips.

Stay cozy out there!
The Heatable Crew

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