A.O. Smith Water Heater won't stay on.


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Old 01-01-18, 07:49 PM
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A.O. Smith Water Heater won't stay on.

I have an A.O.Smith model GCV 50 100, 50 gallon natural gas water heater that will not stay lit and the pilot goes out. I timed it and there seems to be a cycle to it. From cold, I light the pilot turn the gas knob on and it fires for just over 3 minutes, then goes out. The pilot will not light again for about 1 min, 20 sec. Once the gas knob is turned on it fires for just over 3 minutes and so on. It could be my imagination, but I'm pretty sure I hear a click from the contro, unit when I am able to light the pilot again, and i think I am hearing the same click when the burner goes out after 3 minutes, but I am less sure of that click.

Any ideas?
 
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Old 01-01-18, 08:10 PM
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I should add that if I turn down the thermostat to cut off the burner the pilot stays lit and the burner fires again when the thermostat is turned back up.
 
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Old 01-01-18, 08:30 PM
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Series 100 heaters have a cordierite disk that clogs with lint... Try cleaning it... Make a shop vac adapter and vacuum the underside disk through the black air intake screen... No need to remove burner...


https://www.youtube.com/watch?v=6Eml0ar6Bzo

The reason it goes out is because its starving for air,. The t couple has a thermistor that trips the gas off when it overheats... When it cools it resets but you'll be faced with the same thing until you clean it...
 
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Old 01-01-18, 09:10 PM
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A real common problem on the A.O. Smith units. I had the same problem with my 40gallon version. Mike's video shows a home made tool which is how I cleaned mine. This video shows a brush you could buy (you don't need to) but more importantly it actually shows what you are cleaning.

You tube/watch?v=B7Lz8vbNMjQ
 
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Old 01-01-18, 11:45 PM
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They are all made like your video now PJ... The series 100 were the older models. I believe the last year of those were 2006 or 2007... They had a cordierite disk/flame arrestor.. These were round and centered...

But same concept yes....


https://www.doityourself.com/forum/w...water-hot.html
 
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Old 01-02-18, 08:43 PM
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Thanks guys. I made a brush and vacuum tube and got in there the best I could. It seemed like the first firing might have been longer, but it also went out and it too just about as many cycles to get the water to temperature, so I'm not sure it made much of a difference.

Any other suggestions?
 
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Old 01-02-18, 10:13 PM
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Vacuum it better.. check drat hood and all flue pipe for obstructions... Sometimes when then go in a chimney the tiles break and fall and block the flue
 
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Old 01-03-18, 07:24 AM
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Smile

I brushed and vacuumed for about 20 minutes while I was bringing the water up to temp., since I can't see up in there, I just can't be sure I'm getting it. Is there some way to tell if I'm being effective? As I brush, the flame gets more orange in it and I can see debris sparking in the flame. Will it get clean enough that the debris sparks stop? Would that be a good gauge, or will the disk always put off some debris? I take it from the order of your suggestions that the brush and vac is still more likely than a pipe obstruction, so I'll re-vacuum first. How do I check for obstruction? Does soot build up in the pipe? I know it wouldn't be as bad as a wood stove, but is it something I need to attend to?

Thanks for your help.
 
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Old 01-03-18, 07:33 AM
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If you get your head low enough and look into the air vent and up you will see the disk.. Often you will see the layer of dust. The tool I make touches that disk as I vacuum all around it...

Looks like this..

 
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Old 01-03-18, 05:00 PM
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Thanks for the pic. I assume this was from a removed unit, because I can't get anywhere near that angle. It does clear up a question though. I could barely make out that there was some kind of indentation on the screen but I couldn't tell if it was supposed to be there or if it was a problem. I cleaned it out some more before work, but the pilot was out again when I got home, but the burner was staying on longer. I hit it one more time after work and the burner didn't go out until it was at temp. and the pilot stayed, so I have high hopes that I got it this time. ill know in the morning.

Thanks for for all of the help.
 
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Old 01-03-18, 11:05 PM
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You may have to remove the burner and have a look inside... Often rust and stuff or even a broken baffle could of fell on the burner, and burner side of the disk blocking air flow..

I dont think that unit is newer then 2007? It should have the date in the s/n first 4 didgits.. Dont throw money at it as its old.. Spend the money on a replacement if needed..

That was ao smiths first batch of FIVR technology... as you see they had their problems... That disk technology is not made anymore
 
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Old 01-04-18, 07:17 AM
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Unfortunately, it was out by morning. How do I remove the burner? I'm hoping I don't have to replace it. We just bought the house last year. The previous owners installed a second water heater because there is an over-sized tub in the master. The second heater is an electric A.O.Smith. The problem is that they installed it in front of the gas unit and blocking the door. Both will have to come out if the gas unit needs to be changed, so I'm trying to avoid that if at all possible.
 
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Old 01-04-18, 10:38 AM
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Try to look through the window first before you go through the trouble... Make sure you can see blockage, rust, etc etc. It may be clear and its just the disk needs better cleaning..


Also the new pilot assemblies they sell are 200c instead of 180c.. There should be a temp tag on the orange wire there.. Whats it say?

Not that you need a new one, because I am sure its going off on the thermistor..


I did hundreds of these. They are a pain to remove.. But Im a plumber.. If you dont feel comfortable working with gas call in a pro...

Once remove you can get in there and vacuum and such...

https://www.youtube.com/watch?v=nEn5ORCSjS0
 
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Old 01-05-18, 05:06 PM
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While working on this, I found that if the small gauge copper line running from the control into the burning chamber gets bumped near the control, the burner and pilot go out. Is this significant?
 
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Old 01-05-18, 10:07 PM
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Upon closer inspection, I found that the nut was loose. I tightened it and the pilot has stayed lit for a couple of hours so far and still going, however, the water was already at temp, so the burner hasn't had to run much. I'll check it in the am.
 
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Old 01-05-18, 10:40 PM
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That small-gauge copper line is really the thermocouple electrical connection. The nut into the gas control valve must be snug, a bit more than finger tight, to make a secure electrical connection.
 
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Old 02-01-18, 02:20 PM
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Originally Posted by lawrosa View Post
Series 100 heaters have a cordierite disk that clogs with lint... Try cleaning it... Make a shop vac adapter and vacuum the underside disk through the black air intake screen... No need to remove burner...

https://www.youtube.com/watch?v=6Eml0ar6Bzo

The reason it goes out is because its starving for air,. The t couple has a thermistor that trips the gas off when it overheats... When it cools it resets but you'll be faced with the same thing until you clean it...

I just registered to post a big THANKS to you for this and all your other posts on the same topic. We woke up to no hot water this morning and found we had almost the exact same problem with our GCV 50T 100 heater today. I could relight the pilot but it wouldn't stay on, and the main burner wouldn't fire up at all.

When we called out a plumber (before I did my research online) his diagnosis was to look at the manufacturing date (2005) and declare it too old. After finding this site I made the vac tool, cleaned off the underside of the disk, and the heater lit first time and has been on ever since.

I now have a full tank of hot water as well as $2,000 that will stay in our savings instead of paying for the replacement heater we were quoted. I know we're probably going to have to replace it before too much longer anyway, but I'm glad it's not today. Thanks!
 
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Old 11-14-18, 09:14 AM
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My parent's how water heater was doing the same thing, they called a plumber, he re-lit the pilot and blamed the wind. Next morning it was out and they again called the plumber, he replaced the thermocouple assembly - which is not inexpensive on this unit. Still had the issue. I read on this forum about vacuuming the disk from the underside, told my parents I could fix the issue and bought some PVC tubing and vacuumed out the bottom of the disc. Fired it up certain it was going to work. Next morning, no hot water. Not one to be beaten, I pulled out the burned assembly and notice a good amount of soot inside the chamber. Vacuumed the top of the disc and it solved the problem.

I just wanted to make everyone aware the issue couple be due to dust/soot on the BOTTOM or the TOP of the disc reducing airflow for combustion.
 
 

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