A Dearborn heater might fail to light because of a corroded pilot tip, the size of the flame, insufficient gas or a bad thermocouple. Finding out the reason is essential to repairing the heater quickly.
A supply line connected to the gas supply funnels the gas to the tip of the pilot light. The ignition takes place by the action of the pilot light as the gas passes through its tip. A tip corroded with residue over the years blocks the gas from leaving the tip, causing the failure of the pilot light to ignite.
Most of the furnaces have an adjustment element on the pilot light to alter the size of the flame. If due to some reason the adjustment bolt has shifted and the flame size becomes too small to ignite the burners, it could result in the pilot light failing to ignite. Insufficient gas could be another reason for the pilot light not getting lit. Ensure that there is enough gas in the reservoir and the gas supply lines are open.
The thermocouple senses when the flame of the pilot light is hot enough to trigger the ignition. The thermocouple opens the primary gas valve for the ignition of the burners. The malfunctioning thermocouple could be another issue affecting the lighting of the pilot light.