Gas boiler won't stay fired up, pilot stays lit

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Old 02-09-16, 06:52 PM
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Gas boiler won't stay fired up, pilot stays lit




So the boiler won't stay fired up yet the pilot stays on. If I pull out the big red cable in the 3rd picture, from the "Honeywell S86E Intermittent Pilot", the pilot does not go out, however once I plug it back in the boiler suddenly fires up.

Sometimes I do that once and it'll stay going fine for the rest of night or even several days. Other times it takes a few times.

Let me know if any more information is needed. As you can tell from my technical lingo, "big red cable", I have no idea what I'm doing.
 
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Old 02-09-16, 07:11 PM
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Welcome to the forums.

As a new member your post was put into moderation due to the large picture count for a new member without having ten posts. It has been approved. Let me look over your info.
 
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Old 02-09-16, 07:21 PM
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Excellent pictures.

That orange wire is the combination spark ignition and flame sense wire. After the pilot lights.... the flame sensor that sits in the flame senses the flame. There could be one of two problems.

1) The pilot light is not strong enough to keep the flame sensor circuit satisfied or
2) The flame sensor is dirty and needs to be cleaned.....or a combination of both.
 
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Old 02-10-16, 06:58 AM
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Thanks for the response PJmax. I'll see what I can do about cleaning the flame sensor when I get home today.

One question, as my pilot says "intermittent pilot" does that mean the pilot light should be shutting off when it's not heating, and then firing up once there is a call for heat? If that isn't shutting off at all does that mean there is something wrong with that where it's not shutting off the gas valve to the pilot when it should be?
 
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Old 02-10-16, 07:28 AM
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Correct.... as far as I know the pilot shuts off after the call for heat is completed.
 
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Old 02-10-16, 12:05 PM
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<<One question, as my pilot says "intermittent pilot" does that mean the pilot light should be shutting off when it's not heating, and then firing up once there is a call for heat? If that isn't shutting off at all does that mean there is something wrong with that where it's not shutting off the gas valve to the pilot when it should be?>>


Yes, the pilot burner should shut off completely when the burners shut off.


Since it doesn't, measure the voltage from GND to MV/PV. With the main burners off, the voltage should be zero VAC.

IF the voltage there is 24 VAC, you have a bad ignition control.

IF the voltage is zero and the pilot stays lit, you have a bad gas valve which is failing to shut off properly.
 
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Old 02-13-16, 12:59 PM
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Sorry it's taken so long to update. So I misspoke on the pilot, realized that every time I was down there it was cause it wasn't working, so the pilot should have been on. Went down and had someone turn the thermostat up and down repeatedly, and it went on/off as it should have. I can still test it with a multimeter if there is still something that could be wrong there, though would need some pointers as I'm not sure where exactly I need to poke the multimeter into to get a reading.

I took the pilot light/flame sensor thing apart to clean, though it didn't look very dirty.
Not sure what to do next. Could the sensor be bad? Can someone help me find a replacement part? Haven't had any luck searching for a replacement pilot/sensor cord for Honeywell S86e. The red cord in the pics. Also and pointers on how to pull it apart, couldn't get the sensor off of that bracket with the pilot in the picture, though didn't want to force it and break it.
 
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Old 02-16-16, 09:17 AM
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Worst...weekend...ever. Dealing with frozen pipes....so many frozen pipes....completely unrelated to this though (different house). Finally I can focus back on this issue.

Anyone have any ideas/things I can try/check?

Thanks.
 
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Old 02-16-16, 05:35 PM
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Once the pilot lights, the flame rectification system should verify that the pilot is lit within a fraction of a second.

When that happens, the spark ignition should shut off and the main burner gas should turn on.

If the spark continues to operate, the ignition module isn't recognizing that the pilot is lit.

If the spark shuts off and the main burners don't light, either the ignition module isn't switch the main burner on or the 24 VAC to the MV connection on the gas valve IS being made and there is a defect in the gas valve. ( Be SURE that the gas valve is turned to the "on" position)
 
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Old 02-18-16, 11:35 AM
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Spark shuts off. Sometimes burners kick on and stay on. Other times they kick on but then shut off roughtly 10 seconds later. Other times they don't kick on at all till i unplug/plug the pilot/sensor cord. I haven't found any kind of pattern yet so it's a real pain to troubleshoot.
 
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Old 02-18-16, 11:57 AM
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It's almost certainly a bad ignition control module that's going bad.
 
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Old 02-18-16, 12:00 PM
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I would replace the pilot assembly. It will come with a new spark/flame rod.

In the diagram below..... the orange part is the pilot tube. The pilot flame must create a path between the spark/flame rod (red) and ground (blue). Both of those surfaces need to be clean and shiny so that the flame can actually conduct there.

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Old 02-19-16, 08:39 AM
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PJmax,

Thanks so much for the description and picture. You're pretty good at explaining this stuff to someone who is pretty clueless I'll try replacing that since it seems pretty straightforward and is a pretty cheap part.

SeattlePioneer,

What would be involved with replacing the ignition control module? Is that doable or starting to step outside the realm of something I'd be able to muddle my way through on my own?
 
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Old 02-19-16, 10:49 AM
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One other thing is to be sure the ground wire from the control to the burner is clean an tight, often times over looked.
 
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Old 02-19-16, 11:52 AM
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<<One other thing is to be sure the ground wire from the control to the burner is clean an tight, often times over looked. >>



That's not the problem in this case, because the pilot flame is being detected and the spark is being shut off.


<<SeattlePioneer,

What would be involved with replacing the ignition control module? Is that doable or starting to step outside the realm of something I'd be able to muddle my way through on my own? >>


Generally speaking, that's a pretty straight forward job.

But you are very likely going to get an updated part --- not an exact duplicate of the part you have now. That can be expected to take some adaptation.

For example --- the new part is unlikely to have the high voltage connection you currently have. The replacement part typically comes with an adaptor to make the connection to the new part ----but you have to figure out such changes.
 
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