If the pilot stays on, the thermopile and high limit are good. Check for continuity across the thermostat terminals when set at operating temperature. Usually, when you turn the temperature control up you will hear it click on. If the thermostat is good, the gas valve is bad. Replace it.
The thermocouplen is bad .But before you replace it try to reset the hi limit.It you lite and hold for minute and still go out replace the thermocouplen.
Answers & Comments
If the pilot stays on, the thermopile and high limit are good. Check for continuity across the thermostat terminals when set at operating temperature. Usually, when you turn the temperature control up you will hear it click on. If the thermostat is good, the gas valve is bad. Replace it.
The thermocouplen is bad .But before you replace it try to reset the hi limit.It you lite and hold for minute and still go out replace the thermocouplen.