How do you change the thermocouple or flame sensor

Pilot lights over time often form soot buildup on the thermocouple sensor. Try turning gas valve off and use a small metal brush and try to clear the soot buildup. The soot acts as a baffle and the flame cannot heat the sensor properly.

Often the soot builds up in the small orifice the gas feeds through and the pilot flame is not strong enough due to the lack of flame. While you have the gas turned off, try breaking off a metal wire on the brush and reopen the orifice.

Another problem is the buildup of cobwebs on the pilot flame air dilution mixer. Natural gas will not burn unless it is properly diluted with air prior to it burning. So clear any cobwebs away.

After doing the above steps and you have a strong flame and it is hitting the thermocouple real well, the pilot should stay lit. If it does not you will probably need to get a new thermocouple and or a new gas valve.

The thermocouple generates around 17 to 25 microamps of current which is used to hold the pilot solenoid in your main gas valve open.

You may have moved the safety sensor or pilot flame tip. The pilot light heats a wire. The wire is the safety sensor. The wire has to be clean and in the pilot flame near the flame tip.

It more than likely has a bad thermocouple, it is the flame sensor. Some times if you move it a little bit closer to the pilot flame it will work. Also make sure there is no carbon or soot buildup .

What you are referring to is the Thermocouple or Thermopile. What is exactly is the problem?

Does this unit have an OXYGEN DEPLETION SENSOR ? if so, then are you using the heater in an area that is too confined or too closed-up? You say it is forced air, therefore the air must move continuously or the over-heat sensor will stop the gas since there is no air to remove the heat being produced. If this unit has a thermocouple flame sensor, the flame my not be touching thethermocouple sufficiently and the thermocouple thinks something is wrong and stops the gas. Or the thermocouple can be weak and not give a strong signal to allow the gas valve to stay open. This is common on heater and hot water heaters, and you simply change the thermocouple.
Good Luck, Macgivor

all pilots should have a thermocouple to maintain a flame at pilot its the sensor that sends the signal to valve to say theres a flame here i can stay open firstly try tightening thermocouple connection at valve then replace if didn't change a thing and if still playing up change valve this is my usual procedure for pilots and rarley have to change valves but it could be the valve

You need a new thermocouple - or maybe the Pilot flame is not lined up properly to the thermocouple? The thermocouple is a "sensor" that is heated by the flame - which in turn keeps the gas supply to the pilot light on. It the pilot light goes out, then the thermocouple no longer "senses" the heat of the flame, so it turns the gas supply off to the pilot to prevent buildup and explosion.

replace the thermo

Change the flame sensor (Thermocouple) Then go ahead and fire it up. If the flame sensor is not sensing the flame you will be able to light the pilot then everything will shut off. There is a way to agjust the pilot but 99.9% of the time the adjustment is ok, Specially with a floor furnace so change the thermocouple and you will be ok. You can get one at Ace, Home Depot Lowes, or a local appliance store

It's either the flame sensor or the gas valve.

The sensor senses flame and sends signal to the valve, the valve then sends gas through the burner/s.

If it's a thermocouple (looks like thisbefore installed) http://furnaceparts.com/eshop/products/thermocouple.jpg
then replace the thermocouple.
It sits right in the flame pattern and they usually cost less than ten bucks.