I realized 2 weeks ago that there was cool air coming out of my vents when my heat was on. I then figured out that the pilot light would not stay on. I changed the thermo couple and it seemed fine. It would stay lite and the heat was working. Last night I truned the heat on and the same problem occurred. I kept trying to get the pilot to stay lite , but it would not stay lite after I would take my finger off the button. I thought that I may have put in a faulty thermocouple. So... I went to Home Depot and purchased a new one (again). I just got done changing it and it will not work. The pilot light will not stay lit. I have tried SEVERAL times! NO LUCK! I need help!! :confused:

Do you have two wires that set under the thermocouple where you screw it into the gas valve? Some furnaces use a millivolt limit switch that if open the pilot will not light.

There is another key point to thermocouples... the pilot MUST only cover the last 1/2 to 3/4 of an inch at the end of the thermocouple, with the inter-blue part of the flame... any less than the above mentioned points you may NOT develop enough milli-volts of DC to hold open the pilot side of the gas valve open... If all else is correct it is a bad gas valve.

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Originally Posted by T-Top

Do you have two wires that set under the thermocouple where you screw it into the gas valve? Some furnaces use a millivolt limit switch that if open the pilot will not light.

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I do not have any wires under the thermocouple

Do you have a drip loop? A short length of capped off pipe running down to nowhere? If so, shut the gas off and open it up. It job is to catch water. If it gets full, water will put the pilot light out.

I am going through the same problem myself. I have a whirlpool water heater with an FG as the first letters of the model number. Long story short... I replaced my thermalcoupler with no avail. When I finally relented to calling the number on the water heater I found there is a class action suit against whirl pool for the models like mine. They are sending me a whole new manifold assembly kit free of charge. I would check into that if I were you.

Note: Thermocouplers are very cheap and worth trying to fix yourself before calling a plumber.

Just had a similar problem, found out that the theromcouple was not exactly like the original, and I had to modify the clip that holds it next to the pilot light so that the tip was actually in the flame, not just close to it.

You probably already checked that, but since it just happened to me today, thought I'd at least put in a word.

Good Luck!

The "generator" thermopile thermocouple forces 0.25/0.5/0.75 Volt min/typical/max on to the approximately 10 Ohm input resistance of the electrical input to the gas valve that the gas pipe routes through. Use a digital multimeter, about 5~10$ for the bottom of the line DMM, to verify the resistance with the thermopile disconnected, and the 0.25~0.75V with the thermopile tip in the pilot flame. The approximately 0.5 V divided by 10 Ohm = 50mA is enough to hold the small solenoid within the valve closed such that the valve remains open. Any short disconnect or cooling allows the solenoid to release and close the valve and extinguish the pilot. My thermocouple was 20 years old but still good. My valve "generator" input was very high resistance. Disassembling, a broken wire was discovered at the solenoid ground. Simply re-connecting the wire to ground under the little screw fixed the problem, the pilot would then stay on and the pool heater would then turn on the whole burner. Yet another no cost fix of something that the pro quoted big money for, 350$ in parts and 300$ in labor. So much for the big capable don't try this at home pros.