A furnace that has run out of oil can be reactivated by bleeding the fuel line that connects to the oil burner. As the fuel runs out, the furnace sucks oxygen into the filter and fuel line of the furnace, which makes restarting the furnace problematic. A furnace usually displays a green blinking light if the shutoff has been triggered. Once you have a new supply of fuel oil on-hand, you are ready to begin the process of firing up the furnace and getting your home warm and comfortable.
Accessing Fuel Line
Find the screw for the bleeder which is usually situated by the oil pump. Clasp the jaws of a wrench around the screw and loosen it. Tighten the screw back into place by twisting it between your thumb and forefinger. Don't tighten it using the wrench as you will need some slack on the screw for the bleeding process. Connect one end of the rubber tube to the fuel line and place the other end in the aperture of a plastic bottle or a pan. You can check the other end of the tubing during the bleeding process to ensure the oxygen has been fully cleared from the line.
Resetting the Furnace
The furnace reset button is usually found on the unit controller. The button usually has the word "Reset" printed on it and is likely to be green or red. Pressing this button should stop the green shut off light from blinking and activate the bleeding process. In some cases, however, you may have to hold the "Reset" button down for 30 seconds to reset the furnace. This starts the furnace pump working. Loosen the bleeder screw with your forefinger and thumb as you hear the pump starting up.
Bleeding the Fuel Line
Check the plastic bottle as you turn the screw to see if steam is coming out. There will probably be an uneven, frothy spitting as you loosen the screw. This is the dregs of any fuel still present in the furnace. Keep loosening it until it evens out and you have a steady stream of steam clouding up the plastic bottle, with no frothy fuel.
Twist the screw back into place and securely tighten using the wrench. You may have to repeat the process a few times to ensure the oxygen is totally cleared from the line. Once the oxygen has been cleared from the fuel line, the furnace should fire up as normal. You can now add fuel to the furnace and it should work fine.
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