A thermcouple is what keeps pilot on, if your unit has both a thermocouple and thermopile then your pilot CAN stay lit and main burner not come on.do not buy a gas vavle untill you check the thermopile voltage!! very costy blunder.this is how you test it..( open circuit test) Disconnect thermopile leads from valve. take a volt meter set it to millivolts- set it to a mv reading above 500 so that you can test it correctly, my meter has 2000 setting and I use that. connect T/P leads to meter leads.. reading should be 500mv.
( closed circuit test) connect leads of meter to terminals that your thermostat or on/off swich are hooked too, usually top and bottom terminals on most gas valves, turn unit on and reading should be 150mv or more... you need try open circuit. I can test your vavle too if you like keep me posted if I helped or not. 15 yrs experience in gas repairs!!
On your F/p thermopile does not have to work in order for pilot to come on, the thermopile is for allowing gas to flow to burner. replace it at a cheap cost or go with the $$$$$$ gas valve. your unit has both thermopile and thermocouple, thermocouple for pilot, thermopile for burner. It may still be the valve but go with cheapest easiest things first, in all the years i have worked I have replaced less than 20 valves and that is being generous to say that many and I have replaced hundreds of thermopiles and thermocouples
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Hi, the thermopile generator is what keeps your pilot lite, and sends a small amount of electricity called milivolts to the gas valve to open. If the unit will not fire up and the pilot is on, the fault would be in the valve its self. The thermopile is what tells the coil on the main gas valve to open, but if the pilot light lights it is sending the correct voltage (milivolts) to the gas valve coil to open. The valve is faulty and will need to be replaced. Please keep me posted.
Sincerely,
Shastalaker7
The thermopile generator or thermocouple created milivolts to keep the pilot lit. I have been in the heating business for 30 years and more and this is a fact. If in fact the pilot is lit and you have checked the control stat, and all is working properly, then you need to go to the gas valve. The pilot will not stay lit if the thermopile generator and or thermocouple is not working. If you have no pilot, you will need to check them with the correct meter to see if they are indeed putting out the right millivolts.
Sincerely, Shastalaker7
Could it be a gas supply pressure problem? I notice my pilot flame hardly touches the thermocouple and only "grazes" the thermopile. Symptoms are that the pilot frequently extinguishes and when the fire is demanded on by the thermostat there is often up to a ten minute delay before the valve opens and the fire lights up. It will then sometimes shut down for no reason at all, sometimes leaving the pilot light lit and sometimes extinguishing the pilot as well.
Is this a supply problem or is it the gas valve?
Clean the orifice in the bottom of the pilot assembly. That will restore the pilot flame to its original size. It is a VERY small orifice, do not use a metal object to clean. Usually it can be blown out with air.
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The pilot light orifice may be partially blocked from dirty gas supply. Clean the orifice with a fine brush and some compressed air so the flame will heat both the thermocouple and the thermopile adequately. Also re tighten the connections for proper ground also the electrical connections. Al The Handyman Works.
Despite the simplicity of a Millivolt system,troubleshooting them is often not as simple, if you go by the book using a Volt/Ohm meter to test the generator and gas valve. The Pilot Generators are less tricky as they all put out 750 mv or 3/4 of a volt out of the system, in the system is where each result will be specific according to what gas valve is used, not all gas valves have the same ohm's values, and many newer gas valves cannot be ohmed due to the design!
They will read open every one of them.
The way to make it simple and assure you never get any call backs
is to take a AA battery and attach a wire to each end of the battery,
Radio shack sells battery boxes with leads built in for several dollars.
Remove the 2 leads from the gas valve coming from the pilot generator and replace them with the AA battery leads If the gas valve operates normally via battery, it is a good gas valve, if not it is bad.
If you apply voltage to the gas valve and get zero amp draw,the gas valve is bad. Do not leave the battery in place and operate the unit in this manner unless you are able to be diligently watching it, never sleep or leave etc, it is strictly for emergency use or testing.
Old time units had no pilot safety, the pilot valve was manually operated just like a garden hose, if the wind blew it out it still kept coming, however as natural gas is lighter than air it will vent if it is allowed to via the flue, propane units must have 100% safety for the pilots operation as propane is heavier than air and will not vent, it settles in the lowest spot making propane more dangerous in that respect than natural gas is.
750 mv is 3/4 of 1 volt, not much power, the thermopile makes this power by having 2 dissimilar metals co joined in the end of the thermopiles that impinges the pilot flame.
A temperature differential must be maintained across the thermopiles end, if the entire end of the thermopile is hot the power will drop off or stop all together, thus extinguishing the pilot.
Many homeowners make the mistake of setting the thermopile too far into the flame, heating the entire end, not just the top 1/3 portion thinking this will bake it into submission, or force it to make power when in reality it does the opposite.
Despite the simplicity of a Millivolt system,troubleshooting them is often not as simple, if you go by the book using a Volt/Ohm meter to test the generator and gas valve. The Pilot Generators are less tricky as they all put out 750 mv or 3/4 of a volt out of the system, in the system is where each result will be specific according to what gas valve is used, not all gas valves have the same ohm's values, and many newer gas valves cannot be ohmed due to the design!
They will read open every one of them.
The way to make it simple and assure you never get any call backs
is to take a AA battery and attach a wire to each end of the battery,
Radio shack sells battery boxes with leads built in for several dollars.
Remove the 2 leads from the gas valve coming from the pilot generator and replace them with the AA battery leads If the gas valve operates normally via battery, it is a good gas valve, if not it is bad.
If you apply voltage to the gas valve and get zero amp draw,the gas valve is bad. Do not leave the battery in place and operate the unit in this manner unless you are able to be diligently watching it, never sleep or leave etc, it is strictly for emergency use or testing.
Old time units had no pilot safety, the pilot valve was manually operated just like a garden hose, if the wind blew it out it still kept coming, however as natural gas is lighter than air it will vent if it is allowed to via the flue, propane units must have 100% safety for the pilots operation as propane is heavier than air and will not vent, it settles in the lowest spot making propane more dangerous in that respect than natural gas is.
750 mv is 3/4 of 1 volt, not much power, the thermopile makes this power by having 2 dissimilar metals co joined in the end of the thermopiles that impinges the pilot flame.
A temperature differential must be maintained across the thermopiles end, if the entire end of the thermopile is hot the power will drop off or stop all together, thus extinguishing the pilot.
Many homeowners make the mistake of setting the thermopile too far into the flame, heating the entire end, not just the top 1/3 portion thinking this will bake it into submission, or force it to make power when in reality it does the opposite.
Despite the simplicity of a Millivolt system,troubleshooting them is often not as simple, if you go by the book using a Volt/Ohm meter to test the generator and gas valve. The Pilot Generators are less tricky as they all put out 750 mv or 3/4 of a volt out of the system, in the system is where each result will be specific according to what gas valve is used, not all gas valves have the same ohm's values, and many newer gas valves cannot be ohmed due to the design!
They will read open every one of them.
The way to make it simple and assure you never get any call backs
is to take a AA battery and attach a wire to each end of the battery,
Radio shack sells battery boxes with leads built in for several dollars.
Remove the 2 leads from the gas valve coming from the pilot generator and replace them with the AA battery leads If the gas valve operates normally via battery, it is a good gas valve, if not it is bad.
If you apply voltage to the gas valve and get zero amp draw,the gas valve is bad. Do not leave the battery in place and operate the unit in this manner unless you are able to be diligently watching it, never sleep or leave etc, it is strictly for emergency use or testing.
Old time units had no pilot safety, the pilot valve was manually operated just like a garden hose, if the wind blew it out it still kept coming, however as natural gas is lighter than air it will vent if it is allowed to via the flue, propane units must have 100% safety for the pilots operation as propane is heavier than air and will not vent, it settles in the lowest spot making propane more dangerous in that respect than natural gas is.
750 mv is 3/4 of 1 volt, not much power, the thermopile makes this power by having 2 dissimilar metals co joined in the end of the thermopiles that impinges the pilot flame.
A temperature differential must be maintained across the thermopiles end, if the entire end of the thermopile is hot the power will drop off or stop all together, thus extinguishing the pilot.
Many homeowners make the mistake of setting the thermopile too far into the flame, heating the entire end, not just the top 1/3 portion thinking this will bake it into submission, or force it to make power when in reality it does the opposite.
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OK.. This woked great for me.. I have a Gas fireplace. the pilot light would work but would not be able to actually start the fireplace. The thermopile (little point close to the pilot) is not registering enough heat from the pilot in order to engage the gas.. I lit the pilot while holding the gas knob in correct postion. Took a lighter and heated up the thermopile for 5 seconds and turned on the gas. all good and lit p right away. May not be a long standing solution but I only need to light it once a year as it stays on for 6 months.
Jason.
Northern Ontario, Canada
can anyone give me some advise ? my gas fireplace is not lighting the burner. the pilot light is on and when I turn the switch on to light the burner I smell gas and can light the burner with a match and it burns fine.
I will add that at first
i will add that first the burner would partially light and now not at all. as i said when I turn the switch on I smell the gas and can light it with a match. is this the thermopile not working ?
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Thanks I checked it with the leads off and it read nothing. Then I hooked it up and it slwly went up past 500(maybe because it was warm? not sure if it was on the right setting or not my meter didnt have anything marked mv. I was using a 2000m dvc setting. Thanks alot. Arer you located near johnstown pa?
use a lighter to heat thermopile it will tell the switch to open once you heat it up..
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