The oldest way is by a pilot light and over the last 30 years or so these have been replaced by electronic ignition systems.
Gas furnace pilot light on but not firing up.
Pilot lit but furnace not firing.
The tip of the pilot light where the gas comes out and ignites is a haven for collecting soot grime and grit over the years.
M8480 ny i have a weil mclain gas fired two zone hot water baseboard heating system.
The pilot light lights up when the thermostat is turned up.
If gas or propane flow to this pilot light is interrupted even for a moment the pilot light can go out and will need to be relit.
A faulty or dirty ignition or sensor is a relatively easy fix so follow these steps and you may be able to solve the problem yourself.
What else could this be.
Typically about 75 125 labor to replace plus about 10 for the part.
The pilot light or ignition sensor is usually the most common issue when your furnace will not ignite.
Is this a thermocouple issue.
If these fail to do their job your furnace will not come on.
This is why your furnace won t turn on.
It s so small it does not consume much gas.
Thanks for your help.
A dead thermocouple reads as a pilot light blown out but will not always cause the pilot light to go out though it should but does not always particularly on older models.
If the pilot doesn t light on the first attempt wait a few minutes and repeat the procedure this time depressing the reset button for 45 to 60 seconds.
However even many modern furnaces still run pilot lights.
If there is a reset button on your furnace turn the valve to the pilot position and hold a flame to the dedicated pilot gas tube while pushing the button for about 30 seconds.
This is a small flame which is constantly burning inside your furnace.
This is typically the problem if you can hear your furnace click on but it does not fire up.
If your furnace does not have a pilot light move on to the next step.