No Gas Flow From Pilot


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Old 09-25-07, 08:10 AM
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No Gas Flow From Pilot

Pilot doesn't seem to be getting any gas. I can't hear any sound of gas flow. It is a 25 year old furnace with thermocouple. It was working fine a few days ago.

I turned the gas off, moved the selector to pilot, pushed down the button and tried to light it. I thought I would be hearing the sound of gas flowing through, but I don't hear a thing and there is no sign that the pilot is getting gas.
 
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Old 09-25-07, 11:12 AM
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Originally Posted by Steveatus
Pilot doesn't seem to be getting any gas. I can't hear any sound of gas flow. It is a 25 year old furnace with thermocouple. It was working fine a few days ago.

I turned the gas off, moved the selector to pilot, pushed down the button and tried to light it. I thought I would be hearing the sound of gas flowing through, but I don't hear a thing and there is no sign that the pilot is getting gas.

Usually what happens is the pilot burner is dirty or corroded and needs cleaning or replacing. I'm confused, you're saying you turned the gas OFF then tried to light the pilot? Did you mean to say you moved the knob on the gas valve to OFF then to PIlot? Did you wait enough time for the gas to a push the air out of the pilot tubing? Did put a match to the pilot to see if it would light? Gas flow is usually very quiet.
 
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Old 09-25-07, 11:26 AM
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Wink

Might pay to pull the pilot out and clean the orifice and the venturi around it. spiders just love to get in there and block it.
 
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Old 09-25-07, 11:27 AM
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Pilot Not Lighting

When I say I turned the gas off, I meant I turned the pilot light dial to off, waited a minute or so, then tried to light the pilot. I turned the little red dial to pilot, pushed down on it, and then tried to light the pilot. I got absolutely no response in terms of a flame.
 
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Old 09-25-07, 04:13 PM
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Do you have any related information, like - this is the first time of the year you tried to light the pilot, for example?

And you have made sure you have gas coming in from your outside gas source and all valves are open?

You may try purging it several more times without even trying to light it, to see if gas will eventually come out. But then wait like you have been doing before trying to light it, to allow any fumes in there to be drafted out.

If no go, reread post #3.
 
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Old 09-26-07, 06:47 AM
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Good News and Bad News

Thanks to all of your advice, the pilot is now on. I took a can of compressed air, blew it thoroughly onto the pilot orifice and it fired right up.

I have a really great looking flame. I moved the valve from pilot to on. Next I turned on the unit from the thermostat and nothing happens! Stil have the great pilot light working.

Here is what I have tried.

1. Double-checked the valve to make sure it is set on "ON".

2. Double-checked the panels on the heater to make sure they are securely in place

3. Turned the furnace off (there is a switch like one would use for a light running from the furnace to the ceiling).
Waited a while then turned it back on.

4. Re-did the settings on the thermostat about 10 times just to make sure I wasn't screwing something up.

5. Turned the setting on the thermostat for the setting from auto to on. Blower comes on.

6. Checked to see if air conditioner works. It does.

Is the next step to call a professional?
 
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Old 09-26-07, 11:45 AM
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Originally Posted by Steveatus
Thanks to all of your advice, the pilot is now on. I took a can of compressed air, blew it thoroughly onto the pilot orifice and it fired right up.

I have a really great looking flame. I moved the valve from pilot to on. Next I turned on the unit from the thermostat and nothing happens! Stil have the great pilot light working.

Here is what I have tried.

1. Double-checked the valve to make sure it is set on "ON".

2. Double-checked the panels on the heater to make sure they are securely in place

3. Turned the furnace off (there is a switch like one would use for a light running from the furnace to the ceiling).
Waited a while then turned it back on.

4. Re-did the settings on the thermostat about 10 times just to make sure I wasn't screwing something up.

5. Turned the setting on the thermostat for the setting from auto to on. Blower comes on.

6. Checked to see if air conditioner works. It does.

Is the next step to call a professional?
So far, so good. You will now need a voltmeter. You need to see if you're getting 24 volts to the gas valve, if yes then replace the gas valve. if no, then trace the wires form the gas valve back to see where the circuit is open. If it's an older furnace, you should trace back to a high temp limit control. If it's a newer furnace, you will probably trace back to a solid state board. If you have the board, see if you can find a model # and manufacturer name and post that info.
 
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Old 09-26-07, 07:09 PM
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Gas Valve

I wish I had carefully read your message after I got home. Here is what I did.

1. A buddy talked me into replacing the thermocoupler. I thought that the pilot wouldn't work if the thermocoupler was defective, but what the heck. Hard to believe, no benefit. I guess it never hurts to have a new thermocouple.

2. Checked the wires going into the valve. Got voltage. If I had read your email, I guess I should have stopped there.

3. I did a troubleshooting I found on thermostat. No turn on when I hardwired red and white wires.

4. I pulled the wires off of the valve. Using the ohmeter, I checked the stems coming out of the valve and there is no continuity. Not sure if that tells me anything.

5. Based upon your short and simple response, it sounds to me like the valve is shot. Do you agree. Also, is that something I can do myself? It certainly doesn't look like a big deal. Thanks for all of your help!
 
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Old 09-26-07, 07:23 PM
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2. Checked the wires going into the valve. Got voltage. If I had read your email, I guess I should have stopped there.
5. Based upon your short and simple response, it sounds to me like the valve is shot. Do you agree. Also, is that something I can do myself? It certainly doesn't look like a big deal.
Yes, the gas valve is bad since you have voltage to gas valve. How much voltage though? You should have 24- 28vts. at the gas valve. As far as replacing it yourself, it sounds like you have enough aptitude to do it so go for it. Just make sure you get your gas pipe fittings tight and do a good leak search.
 
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Old 09-27-07, 06:44 AM
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Gas Valve Voltage

sgthvac, thanks for the information. I am getting voltage ranging from 24 to 28 when I put the meter on it. Sounds like it is definitely time for valve replacement!
 
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Old 09-27-07, 02:41 PM
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If this was me, I'd want a confirmation that gas is not able to come out the burner side of the gas valve. That there isn't some obstruction before or at the burner. Too many times people do what seems obvious, to only exclaim in disgust later, "What the......?!!"
 
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Old 09-27-07, 03:42 PM
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Originally Posted by ecman51`
If this was me, I'd want a confirmation that gas is not able to come out the burner side of the gas valve. That there isn't some obstruction before or at the burner. Too many times people do what seems obvious, to only exclaim in disgust later, "What the......?!!"

good point 51, since the pilot burner was dirty, check the main burner orifices and the burners themselves first to make sure they are clean and not obstructing the flow of gas.
 
 

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