How to Troubleshoot an Oil Boiler With No Cold Start

Resetting

• Oil boilers come with a reset button for restarting the entire combustion control panel. Sometimes glitches keep the boiler from starting correctly, and resetting the entire system can solve the problem. This button may be positioned on the primary control board or on the burner motor itself. Push the reset and then wait for the furnace to come back on and stay on without suddenly shutting down. Do not push the button more than three times, since this can activate a lock-out.

Circuitry

• If the reset button does not work, the problem may lie with the circuitry itself. It is time to test the motor on the burner assembly that helps direct the oil and the ignitor itself. If these parts burn out or their wiring fails, the burner will not be able to start. Replacing these parts is the only way to fix the problem, so be certain when you're narrowing down the failed part.

Sensor Problems

• Oil boilers have sensors made from ceramic disks that detect errant oil flames in the burner. If these sensors, called cad cells, do detect flames, then they will break off circuits and shut down the burner completely. If the thermostat is working properly, the cad cell may have failed. Small cracks in the burner housing can also let light in and cause the cell to think the light is flame and shut down anyway.

Fuel Problems

• A poor start or no start at all may also indicate problems with the fuel. The oil boiler needs oil and air to ignite properly. Clogs in the oil lines and dirty oil filters may cause problems. Air supply vents can also become filled with debris or blocked by snow. Clean the system, remove any blockages or corrosion, and try using the burner again.