good igniter, intermitent flame


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Old 02-14-10, 07:28 AM
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good igniter, intermitent flame

Cant see a brand name it is a mobile home gas. all it says on label is "direct vent forced air" mod num dgat070bdc

controller info is
robert shaw hs780 34nr - 306a


vent moter starts, igniter glows, sometimes flame, sometimes not. seems to quit more at night. vent moter will continue to run and igniter will come on everyso often ect. it also seems like it take quite awhile for the main blower to come on when there is flame

i think it is either control valve or controler cannot afford to get wrong part thanks
 
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Old 02-14-10, 09:00 AM
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Might want to remove the gas valve and brass orifice connected to the stub on the valve. Look in the stub and see if there is an insect cocoon in there. Have seen it many times and it will impede the gas flow.
 
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Old 02-14-10, 01:12 PM
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Originally Posted by smoke42075
it also seems like it take quite awhile for the main blower to come on when there is flame
If the blower comes on by heat, the colder the mobile home gets, the longer it will take for the blower to come on. If the burner flame is proper though, it should come on by no longer than about 1 1/2 minutes anyway.

Test your HSI to see if the ohms are within range of it being good. About 100 or less, on your volt-ohms meter set to ohm.s Also, I'm not sure what you maybe do when it sometimes does not come on -but then maybe does come on, sometimes. If you are resetting it, it could be a flame sensor causing your problem. Always good routine practice to clean a flame sensor, regardless, maybe every couple years. And if real or relatively easy to do, I'd do it prior to each heating season, actually, for some piece of mind.
 
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Old 02-14-10, 01:34 PM
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Old 02-25-10, 03:41 PM
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does the flame sensor tell the gas control to kick on by detecting heat from igniter? could the temperature switch influence main blower. I wish this one had some blinking lights
 
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Old 02-25-10, 04:16 PM
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Flame sensors tell furnaces to shut off - not to come on - since you have to have flame first for the flame sensor to sense the flame. IOW -they do not sense something prior to the flame and then send a signal to the gas valve.
 
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Old 02-25-10, 04:20 PM
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some clicks

I would say it makes three differnt levels of clicks

first when i turn power on the med click" exhaust fan and igniter come on"

lighter click right before gas kicks and when it does the loudest click being the gas, if gas doesnt come on i get the med click again and the ignighter shuts off and exhuast fan runs untill it does it all over again

Is there a test procedure for gas valve
 
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Old 02-25-10, 04:27 PM
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Its either the ignition control or gas valve. I am hoping that the clicks can help someone help me out here. its either 100 or 190 for the respective parts
 
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Old 02-25-10, 04:28 PM
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Originally Posted by smoke42075
vent moter starts, igniter glows, sometimes flame, sometimes not.....vent motor wil continue to run.
Thatr isa al one needs to read to, right there.

Could be the ignitor is weak, even though it glows. Test across the two wire leads of the HSI hot surface ignitor) to see if you have an ohms reading under 100.

The vent motor continuing to run, shows at least your stat is still calling for heat, so we can rule out the stat.

Also let us know if you hear a click of a gas valve. Even if the HSI is weak, the staging is still set for the gas valve to open. You can also feel the gas valve click when you touch it with your fingertips. No click or no 24 volt at MV terminals on gas valve can show bad electrical connections or bad board. But if there is a click, and 24 volts at gas valve(which there actually would be, if you hear or feel the click), then it can be bad HSI or fuel blockage not letting full gas flow to get to HSI quickly enough.
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Hmmm. Just read your last 2 posts about the clicks. Feel them to determine if it really does feel and sound weaker. And you maybe better voltmeter test during both situations of flame coming on, and not coming on, to see what it reads for each. Also test the gas valve wires with the gas valve wires disconnected to rule out a short that could otherwise lead you to a false assumption as to wherein lies the problem.
 

Last edited by ecman51; 02-25-10 at 04:35 PM. Reason: added even more to last paragraph
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Old 02-25-10, 04:32 PM
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when i do hear gas valve i get flame. sometimes gas valve does not click
 
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Old 02-25-10, 04:35 PM
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will check back tommorrow after getting some readings. I dont have meter here right now. if it makes any diff igniter was replaced earlier this year
 
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Old 02-25-10, 04:54 PM
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Never make assumptions based on when a part was replaced. Testing is more absolute. So actually test the HSI. But it does sound the way you describe the clicking, that something else may be at fault.

I'll (and likely "we" all interested parties visiting here) be waitng for your test results. Remember - with wires off the gas valve at least for some of the tests, to eliminate a possible volt drain by say a faulty gas valve's solenoid -or if a lower reading is really coming from a bad board, or bad connection at the board. And many tests have to be done to rule out coincidences that the furnace would or wouldn't have fired up, if the wires were attached.
 
 

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