can't adjust pilot light


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Old 12-17-10, 01:48 PM
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can't adjust pilot light

I have an old Lear Seigler furnace in a mobile home. It has a Robert Shaw controller model 700. My pilot light is over an inch longer than it should be and everything past the thermocouple (which has just been replaced) is bright yellow. I know it should be shorter and blue. The pressure regulator screw doesn't seem to change the length of the flame and either way I turn the pilot screw, nothing changes. The burners were over firing (brighter, yellower, hotter) about once every 5 or 6 times.
It's getting colder in North Dakota and I'm sure I'm wasting gas and want this running as efficiently as a 40 years old furnace can. Thanks.
 
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Old 12-17-10, 02:34 PM
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Are you sure you are adjusting the right screw? (Usually under another screw head located near the gas tubing for the pilot.) If you are turning the correct one, and the pilot's size doesn't change, replace the fuel valve.
 
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Old 12-17-10, 05:25 PM
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Originally Posted by Domino53
I have an old Lear Seigler furnace in a mobile home. It has a Robert Shaw controller model 700. My pilot light is over an inch longer than it should be and everything past the thermocouple (which has just been replaced) is bright yellow. I know it should be shorter and blue. The pressure regulator screw doesn't seem to change the length of the flame and either way I turn the pilot screw, nothing changes. The burners were over firing (brighter, yellower, hotter) about once every 5 or 6 times.
It's getting colder in North Dakota and I'm sure I'm wasting gas and want this running as efficiently as a 40 years old furnace can. Thanks.
Sounds like the pilot really needs cleaning. Are you able to blow back thru the opening where the flame comes out. You must clean before attempting to adjust, it may not need adjusting once cleaned. Just taping the pilot may clear it. I really hope you haven't changed the pressure, could be putting yourself in danger with an overgassed furnace.
 
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Old 12-17-10, 06:04 PM
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Time to call in a professional. You could have high gas pressure & without a manometer there's no way to tell. Any other gas appliances in the home? If so how does the flame look on them?
 
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Old 12-17-10, 06:25 PM
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I agree with Grady. This furnace is past due to have the needed maintenance work done on it.

Very likely the pilot burner, main burners and fan need to be cleaned and the vent and furnace checked for safe operation.

That's probably no more than an hour of work.

That kind of jobs requires good judgment and a variety of skills to do and is usually not a suitable task for a do-it-yourselfer.
 
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Old 12-17-10, 06:28 PM
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I had a professional clean out the pilot light a couple of days ago. I've tried adjusting both screws, the pilot screw and the gas pressure screw. The flame on both the pilot and when the burners over light seem like a lot of pressure so I've tried both. The pressure I've only turned down, not up. The instructions on the RobertShaw gas control says turning the screw counterclockwise decreases pressure. I've only turned it that direction and less than half a turn. No other gas appliances in the house. Could the guy who cleaned out the pilot reamed it out larger than before?
Also, the term professional in rural North Dakota is pretty loose here. The guy I had work on it a couple of days ago IS the local heating professional. And he blew me off on a lot of my questions.
 
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Old 12-17-10, 07:04 PM
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Find someone else to help you. I see nothing to suggest this is suitable for DIY repair.
 
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Old 12-18-10, 09:51 AM
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Are you able to send any pictures??
 
 

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