Learn how your appliance is supposed to operate so you can determine if it is malfunctioning.
The radiant sensor is designed to detect the heat from either the ignitor or the burner flame. It is basically a bimetallic switch or thermostat. Its contacts are normally closed and designed to open when it detects the radiant heat of a fully glowing ignitor or burner flame.
Once the radiant sensor detects that, its contacts open which forces power to the ignitor to go though the burner valve's secondary coil first. At that time the secondary coil opens the gas valve but at the same time deenergizes the ignitor which gradually begins to cool. Since the ignitor takes some time to cool, the escaping gas is still able to ignite on the now just slightly cooled ignitor, to produce a flame. The radiant heat of that flame keeps the radiant sensor's contacts open.
If the radiant sensor's contacts remain closed the whole time, the ignitor will never shut off and no power will get to the secondary gas valve coil (see illustration below) for it to release gas into the burner to be ignited.
Use the appliance model number to order the correct replacement radiant sensor.
All of the information in these Appliance Clinic procedures is provided FREE OF CHARGE. No liability is assumed by the author for the accuracy of the contents or damages caused by the use of these procedures.