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 Posted: Thu Jan 19th, 2006 04:03 pm
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core
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Greetings!

First let me say that I have read ALL relevant information on this site, including all relevant-sounding forum posts going back to the very inception of the board.  Based upon these very informative posts (thanks guys), I have a pretty good idea what's wrong.  What I'd like to know (and for the benefit of the searhable archive) is what I might be able do about it myself.

In short, the situation is that suddenly in the last couple of days my standing pilot light has refused to stay lit for any length of time.  This is not sporadic; I _believe_ it always extinguishes itself sometime after the first cycle, but I have not 100% verified that -- hope to do that sometime today.  My first thought was to run out and buy a new thermocouple, but after spending much time reading on this site and doing some troubleshooting, I think that would be fruitless.  (See below)  There have been no environment nor plumbing changes in my house.

When lighting the pilot it does not always light right away, but then again the selector knob was a bit sticky on this old heater when I went down there so who knows.  When I press down on the selector to engage the pilot gas I do NOT hear the gas (even though the pilot does eventually light).  During the lighting process it does not always stay lit, but using a match to heat the thermocouple for several seconds usually gets the job done.  I have left the thing alone for 30+ mins while it was recovering and came back and turned the thermostat down to vaction:  pilot stayed on fine for the several seconds seconds until I cranked the temp back up and the burner fired up again.  (Silly me:  Probably should have left it down for a few mins to see if it went out eh?)  

The pilot flame is basically on the thermocouple, although it is not totally wrapping around it.  The t'couple is not "glowing red" as mentioned in other posts but then again I've never seen one that has.  (LOL maybe I'm just used to looking at failing stuff.)  The strange thing that I have not seen mentioned is that my thermocouple has a white residue on it, almost scale, right where the pilot flame touches it.  I'll post pics here shortly if the forum permissions allow it.  I never did quite understand _exactly_ what it should look like when you experts said 1/2" of the end of the thermocouple and "partially" wrapping around it.  

I'm assuming gas pressure is pretty much ok because my furnace and gas dryer are working fine.  The burner emits a nice blue flame with only an occasional lick of yellow, but then again I don't have an eye for exactly how it's supposed to be normally.  There doesn't seem to be any downdraft/heat out of the flue hood or whatever it is called.  Venting is nearly straight up through a skinny brick 2 story chimney, lined with small ducting.  The chimney used to be shared by the furnace (2+ years ago) but isn't any longer.   I haven't lived in this house for many years, but based on the heater label it was either made in 1983 or 1985 (hey, I'm not complaining at ALL!).  But it couldn't have been installed here back then because the whole area was totally underwater during the great flood of '93.  There are still bits of solder on the anode hex nut which tells me the anode has not been replaced since installation.  I guess I'm lucky the thing still works at all without any leaks.  Good thing my T&P valve is stuck shut so I don't get any water on the floor.  (No just kidding!!!! Haven't tested it yet but CERTAINLY will today after seing that pic of the 5 gallon heater explosion in the school).

Anyway, what all of this tells me, as a non-plumber, is that the thermocouple is fine but it's not getting heated properly.  The "scale" I mentioned above:  Can I just scrape this off with a knife without damaging the thing?  That's gonna be my first step I think.  Based on other posts I'm getting the feeling that my pilot flame isn't quite what it should be, and even though the residue indicates it's been "about" the same all these years, maybe it has just crossed the line to "not quite enough".  The owners of the site have said two different conflicting things:  1)  Clean the orifice out, and in a different post it was said that 2)  It takes a carefully trained eye to clean these.  I certainly don't have a carefully trained eye, but am going to attempt it anyway if that's what might help.  I did read about the guy who "reamed"(??) the orifice out until it yielded a 4" pilot flame -- I will certainly be careful, and don't plan on using any heavy-duty tools.  Maybe just a little eyeglass screwdriver to scratch out any obvious obstructions.  Anything I should do or watch out for?  Will CLR or a similar solvent help without doing any damage?

Thanks in advance for those answers!


P.S.  On a more frivolous note, would it do ANY good to buy a new anode?  This is a State Courier and the hex head is flat so I'm guessing it's aluminum.  (Or WAS, before it no doubt totally disintegrated.)  I'm rightfully concerned about aluminum but I'm not drinking out of my hot water heater and don't know anyone in their right mind who would, so I guess that's not so much of a concern.  But I would like to keep this old beast running as long as possible.  Not for economics' sake (I know it will cost me much more), but just to see how long I can keep it alive, on principle.  21-23+ years is pretty good for something that's been totally neglected!

Thanks again!

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 Posted: Fri Jan 20th, 2006 06:51 am
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eleent
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Hello:  I can't explain the mechanism, but thermocouples do wear out.  The right test would involve getting tools that cost a good bit more than a thermocouple.  The symptoms do indicate poor output from the thermocouple, so I'd start by replacing it.  It has done well to last so long.

Next is to look into the combustion chamber with a flashlight and carefully examine the roof of the chamber (bottom of tank) and bottom of the flue.  If you find these dry and without serious rust, go ahead and replace that anode.  You'll never get the tank to make it to over fifty years (I've had some good luck with heaters) if the anode isn't changed.  When you do that, you might want to remove that plug from the relief valve too :D (or just install a new valve).

Price a new heater.  It will help motivate you to keep this one going!

Yours,  Larry

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 Posted: Fri Feb 17th, 2006 04:20 am
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core
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As I feared, a new thermocouple did not help.  The only difference now is I don't have to hold the match on the t'couple to get it to initially heat up -- presumably this is because the new one is more sensitive. 

But the heater still goes out even before a complete cycle.  I put a video camera on it this last time and even with the full burner on, the whole thing went off after just 5 minutes.  Burner & pilot both at the same time.  Normally it stays on for 15-20 mins, but this was my second attempt of the day.  Always seemed to go off quicker when things were things were still somewhat warm.

I had planned on cleaning out the pilot orifice while replacing the thermocouple but after yanking the whole assembly out I see it is VERY small.  Some fine electronics wire is about the only thing I can think of that will possibly fit in the hole.  Ooohh just had an idea though... maybe some carb cleaner?  With a very thorough rinse and plenty of drying time afterwards?

What made me think this is a pilot problem rather than the t'couple is that the pilot was very difficult to light and stay lit even with the button being held down.  And I have to put the match flame right _on_ the opening -- close does not do it here.

Also possibly related:  When I put everything back together I did the Windex test as recommended on this site.  There is a _very_ slow gas leak near the gas control on the pilot gas tube.  Seems the last person to screw around with this heater got a little overzealous with a pair of pliers and squeezed the actual tube a bit instead of just the fitting, causing the fitting not to seal perfectly.  Though I will replace it when I can I'm not too worried about this -- been that way for years and it certainly never affected the heater's operation nor caused a detectable amount of ambient gas.

I guess unless anyone has any better suggestions my next steps in order are going to be:
1. Clean pilot orifice with carb cleaner and whatever small wire I can find.
2. Replace whole pilot assembly and the gas tube leading to it
3. Assume it's the control and consequently ditch the whole darn heater.


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 Posted: Fri Feb 17th, 2006 07:23 am
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eleent
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Hello:  Maybe cleaning the pilot orifice is a good idea, though I'd stick to chemical cleaning rather than a wire. There should be sufficient heat to make the tip of the thermocouple glow dark red. Beyond that, when video-taping, what happened when the pilot went out?  Did a drip of condensation hit it? Did the pilot flame float off the burner and go out? Did a breeze get it?  Did a furnace connected to the same flue come on? Did the main burner flame push the pilot flame away from the thermocouple?

There must be a cause you can see.  Try lighting it and then sitting with it to see exactly what happens.  If it goes out, light it again right away to keep the tank heating. See if it will get up to temperature and then stay there.  Watch the main burner to see than it is behaving properly.  That is, not lifting from the burner, not floating, staying mostly blue...
It could be a problem with the vent or supply air rather than with the heater.  If it were the main control, it would likely not stay lit at all.  The truth is out there :cool:.

Yours,  Larry

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 Posted: Fri Feb 17th, 2006 07:01 pm
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core
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I tried your suggestion about immediately relighting it to get it up to temperature.  Unfortunately it will not light at all right now (it's warm).  Pilot doesn't even _try_ to stay lit... as soon as I release the pilot button it goes out.  The pilot's definitely not getting gas right now unless I hold it.

Before that, I did another test (with everything cold from sitting overnight):  I lit the pilot and left the selector knob on the Pilot setting.  The thing stayed on fine no matter how many hours I left it! *gasp*   Now I'm very confused! 

-core

Last edited on Fri Feb 17th, 2006 07:08 pm by core

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 Posted: Fri Feb 17th, 2006 09:23 pm
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core
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Problem isolated!  Not that I'm overly happy about it.  In short:

Warm water in tank (> 115 F) equals gas gets temporarily shut off.

I've spent many hundreds of gallons and many hours eliminating all other variables, this is it.  The sticker on the control says that the high temp cutoff is a single use, non-recycling type.  So that little doohickey probably isn't it.  Not that it matters -- doesn't sound like this is something _anyone_ is going to be able to fix without wasting $100 on a new control for a very old heater?  Darn.

If I leave the thermostat just above Vac.Low such that it doesn't get near 115F then everything's fine.  Lukewarm showers are more tolerable than relighting it a half hour before I need hot water!  Guess I can deal with that (and the legionella!) for the time being.

-core

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 Posted: Sun Oct 30th, 2011 01:20 pm
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Kent
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Hi,
I am trying to clean my pilot light and not sure what chemical solution works best. Please let me know what to use. Thank you! :)

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