Weird, pilot light worked then didn't,then worked.new thermal couple

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  #1  
Old 10-16-11, 05:01 PM
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Weird, pilot light worked then didn't,then worked.new thermal couple

I replaced the TC, the pilot would stay lit (all was fine) with my furnace then it would go out after the burners went off. I'd relight it, it would stay lit for a while then would go out. The pilot seems strong when in pilot position and it seems to run smooth when burners are on. When in pilot position, it seems to have an issue.

Bills is paid...lol
Any help would be greatly appreciate.
 
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  #2  
Old 10-16-11, 05:22 PM
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the gas valve could have a weak coil... or the pilot is getting blown out by a bad heat exchanger. I would start be removing the pilot and cleaning the pilot burner and orifice.
 
  #3  
Old 10-16-11, 05:29 PM
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I did about a month or two ago. Let me know describe, maybe I missed something. I unscrewed pilot from valve and the clamp that is connected to thermal couple and removed the little cap tip that fuel comes through. Then I blew them both out to make sure they were free from dust and debris. I did notice blow back when the burners light. Not a lot but still there's a little that ignites when the burners come on. I don't have access to a compress in my house to I'm limited to a compressed air keyboard duster for blowing items out.
Thoughts?

Thanks in advance.
 
  #4  
Old 10-16-11, 05:34 PM
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If the pilot is strong and it still goes out it could be a bad Gas Valve or a failed heat exchanger that is blowing the pilot out. Hard to say without being there. A video might help if you have the capability to post one to you tube or something.
 
  #5  
Old 10-16-11, 05:41 PM
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Be back in a few. I'm going to get a vid...great idea.
 
  #6  
Old 10-16-11, 06:13 PM
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Here you go. It's a little long but you get the gist...


http://www.youtube.com/watch?v=3nmcAsuuy5E
 
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Old 10-16-11, 06:25 PM
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Sorry it's sideways. It will correct itself in a few minutes.
 
  #8  
Old 10-16-11, 06:30 PM
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so according to the video the pilot will not stay lit? either the T-couple is not screwed in all the way/properly or the t-couple is not being engulfed in the flame properly, or the gas valve is bad. Check the first 2, the third would require a meter.
 
  #9  
Old 10-16-11, 06:35 PM
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Ok:
1. Screwed into the valve all the way? (is that what you meant)
2. So should I readjust the couple and if so, should the flame engulf the tip or middle?
3. I'm pretty hand and techy and I have a meter, so I'd be able to determine the valves condition. (ohm reading?)

Thanks a million
 
  #10  
Old 10-16-11, 06:46 PM
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flame should be in the top 1/3 to 1/2 of the t-couple Disregard the gas adjustment the pic talks about.
 
  #11  
Old 10-16-11, 07:40 PM
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still...

Ok, I removed the couple and pilot: made sure pilot was clear and adjusted the couple and pilot to ensure proper flame coverage. I adjusted the pilot down a hair to ensure it was covering as much as needed. The pilot stayed lit for about five seconds then made a click sound and went out. I did notice that the tip of the couple was glowing red, so I readjusted a hair and it no longer glows red.
i made sure all the connections were tight for the pilot.

Any thoughts?


Originally Posted by hvactechfw View Post
flame should be in the top 1/3 to 1/2 of the t-couple Disregard the gas adjustment the pic talks about.
 
  #12  
Old 10-16-11, 08:00 PM
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make sure these connections are good. Unthread the t-couple, the device that the wires are hooked to in the picture, sometimes that device can be removed from the gas valve. They sometimes go bad. Because your furnace does not use that device for a limit it can be removed and the gas valve can be used with out it. IF you can get that device out then reinstall the t-couple into the gas valve. This may remedy your problem.

 
  #13  
Old 10-16-11, 08:36 PM
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Ok, I unscrewed the T-coup and the mechanism that the t coup screws into. There is a plate that sits under there in which the two contacts that the jumper wire connects to. Do you want me to remove the plate underneath the cap that the t coup screws into and then reinstall the cap that the t coup screws into. I turned the gas off but after removing the cap I smelled gas.
here's a pic of the cap and the plate underneath the t coup.
 
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Old 10-16-11, 08:40 PM
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didnt get the pic. not sure what you are talking about when you say cap. Try to repost the pic or just post the link to the pic.
 
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Old 10-16-11, 08:40 PM
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  #16  
Old 10-16-11, 08:42 PM
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I can not view your pics. you may have to change who the pics can be viewed by from friends only to everyone.....
 
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Old 10-16-11, 08:45 PM
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by cap i just mean the actual part that the t couple screws into. I removed the little silver plate underneath that (it looks like a quarter and has a contact on it) then I reinstalled the cap (item mentioned above)
Is that what you meant?
 
  #18  
Old 10-16-11, 08:50 PM
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no, that is not what I meant. Where the t-couple screws into the gas valve, in my picture it is the part with the jumper wire across the terminals, that pat can most of the time be pulled out and not used.... it is often white plastic with metal contacts on both sides..... Please try posting your pics to a site like google or photobucket.
 
  #19  
Old 10-16-11, 08:51 PM
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try again. If that's what you meant, I did remove that little silver plate and tried again. still no pilot. should the t coupl glow red? is it possible that it's not heating up enough?
 
  #20  
Old 10-16-11, 08:53 PM
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red is plenty hot enough..........

if you removed the little silver plate what about the piece that the jumper wire is attached to? has that assembly been removed?
 
  #21  
Old 10-16-11, 08:54 PM
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ok, so just that plastic piece that actually has the bottom terminal connected to it should come out and the silver plate with the gasket and the cap that the t coup screws into all goes back together?
 
  #22  
Old 10-16-11, 08:56 PM
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never mind, looks like you need a new gas valve.
 
  #23  
Old 10-16-11, 09:00 PM
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no, when i removed the silver plate the piece under it seemed more permanent. it could possibly be stuck, or is it connected by a tiny screw i see in the back? should I wiggle it a bit to try and free it up?
 
  #24  
Old 10-16-11, 09:01 PM
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nope, I didnt tell you to unscrew anything but the t-couple. some of those valves have the ECO device installed in a different location from where yours is located on your valve. You need a new gas valve.
 
  #25  
Old 10-16-11, 09:03 PM
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ok, thanks for all the info. do you know the reading so I can test the valve? I have a meter.
 
  #26  
Old 10-16-11, 09:10 PM
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with everything put back together, you need to remove one lead of the jumper wire across the ECO device and insert your meter lead there and put the other meter lead on the terminal that you remove the jumper from. Set you meter to DC mV. With the pilot lit you should get a reading around 25 - 30 mV.
 
  #27  
Old 10-16-11, 09:20 PM
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it doesn't matter if I have to hold the light button down to keep the flame lit, it should still read 25-30 mV...correct?
If so, I got 2.1-2.9
 
  #28  
Old 10-16-11, 09:23 PM
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my meter is a bit old so it didn't actually have the DC mV setting, it had DCV- 200m setting. Which I believe is the same?
 
  #29  
Old 10-16-11, 09:24 PM
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no, you will have to hold it down during the test.
 
  #30  
Old 10-16-11, 09:30 PM
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you need a new gas valve........
 
  #31  
Old 10-16-11, 09:34 PM
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Ok, I'm going to grab one tomorrow. Thanks again.
 
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