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Discussion Starter #1
The hvac guy charged me $365 to replace control unit on my boiler...it looks used and he brought it from his van out of the box. Now the pilot won't stay on. I've already replaced the thermal couple (sp?) so now he tells me I need a new gas valve which will cost another $365. Iis this true or could the problem be the bootleg control unit thats causing the pilot and burners to malfunction?
 

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Send pictures. Info is vague. Gas valve may be faulty but....
Does the pilot stay on until the mainburners ignite or does the pilot light go out when you release the gas valve control.
Is the thermocouple in the pilot flame? Is it properly screwed into the gas valve? Does that gas valve have properly attached jumper connections to an ECO? Are you giving it at least a minute of flame time before releasing the gas valve control? Have you an electrical meter to test the new thermocouple dcmv output after a full minute of pilot flame?

Boiler gas valve pilot solinoids (run by thermocouples) are electrically independant from all other controls. A faulty control can affect the main burners but not the pilot.
 

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Discussion Starter #3
The pilot stays on but goes out with the burners after a while, and I have to relight the pilot to fire up the boiler. The control unit was replaced about two weeks ago. I don't have a meter to test electrical output.
 

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That control may have been on his truck in that box for a long while. But be brand new. Can't tell you for sure though.

It could be your gas valve is going out, or your pilot flame is too small or too big. Have you cleaned the pilot burner?
 

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Discussion Starter #5
That control may have been on his truck in that box for a long while. But be brand new. Can't tell you for sure though.

It could be your gas valve is going out, or your pilot flame is too small or too big. Have you cleaned the pilot burner?
On the truck awhile but still brand new? Uh that dont sit well with me...for $365 I want out of somebody's inventory that mfg'd it not an old stale part off the truck. Is this normal for this industry? To sale old parts as new?
:eek:
The pilot was cleaned when the thermal coupler was replace about a month ago. It was also replaced last year. Is this something I need to do every year?:eek:
I've always had forced air so I'm not familiar with this type of furnace do parts go bad all at once?
 

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AKA HVACTECHFW
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A new part is a new part. If he didn't have the part on his truck it probably would have cost you even more if he had to go get it or make a second trip back after the part came in. Sometimes you have to make an initial repair to get to a point in the diagnostics process to determine that another part is needed. Such as there is a sequence of events that take place when a furnace receives a call for heat. If step 2 doesn't happen then you never make it to step 4 & 5 to know if there is a problem at 4 & 5.
 

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Discussion Starter #7
A new part is a new part. If he didn't have the part on his truck it probably would have cost you even more if he had to go get it or make a second trip back after the part came in. Sometimes you have to make an initial repair to get to a point in the diagnostics process to determine that another part is needed. Such as there is a sequence of events that take place when a furnace receives a call for heat. If step 2 doesn't happen then you never make it to step 4 & 5 to know if there is a problem at 4 & 5.

I see thank you. Well so far the control unit, thermal coupler and a switch have been replaced just seems odd that everything went bad all at once. Of couse service calls charged each time thats why I'm wondering if the boiler needs to be replaced altoghter. What do you think?
 

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It sounds like your burners and pilot are being starved of oxygen. Is there a door with a clogged vent screen or something?
 

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Discussion Starter #9
It sounds like your burners and pilot are being starved of oxygen. Is there a door with a clogged vent screen or something?
I can feel the air coming thru the door vent. It's getting air. The
Burners were cleaned when the coupler was replaced.
 

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AKA HVACTECHFW
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I see thank you. Well so far the control unit, thermal coupler and a switch have been replaced just seems odd that everything went bad all at once. Of couse service calls charged each time thats why I'm wondering if the boiler needs to be replaced altoghter. What do you think?

I can't tell you that.... only you can make that decision. However, in order for you to make an informed decision you need to do your homework and explore replacement cost from several contractors in your area vs what you have already spent in repairs and what any future repairs might cost you. You should also weigh into this decision the age of your current boiler, the efficiency of a replacement vs what you currently have, and look at warranties. If you do decide to replace get references! A bad installation will make the best boiler out there not last as long as it should. Installation is much more important than brand.
 

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If the pilot is going out, after the main burners have been on for a while...

Look to see if the cold junction of the thermocouple is resting against the bottom reflecter plate of the boiler. (Causes the thermocouple dcmv to drop)
Watch to see if the draft being drawn into the boiler is pulling the pilot flame off the thermocouple. (the pilot flame is too soft)
Watch to see if any of the flame on the main burners is floating just above those burners. (The heat exchanger needs cleaning or the unit is overfired)

Then it's thermocoupler testing 101

That technician should put an adapter in between the thermocouple and the gas valve to do a real time dcmv reading while the boiler is at rest and when it's firing.
When the burners are not firing, you need the normal closed thermocoupler dcmv reading and the time & dcmv output it takes for the pilot solinoid to drop out when the pilot is extinguished to see what the problem really is.
Then the reading of the thermocoupler output when the burners are firing. (for at least the length of time it was taking the pilot light to fail.
This will tell you if the pilot outages are from the thermocouple/ thermocouple pilot solinoid/or boiler conditions.
 
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