# AO Smith GPSH water heater in System Lockout mode



## Abs777

I have a 5 year old AO Smith 'GPSH with Hot Surface Ignition' water heater that will not heat water. I will cycle the power and when it comes back on the fan will run for a less than a minute then kick off, then run for less then a minute and kick off, then it goes into System Lockout. 

I checked the manual and it states these could be the issues

1. Gas supply is off or too low to operate - gas is on and working to stove and fireplace
2. Hot Surface ignitor not positioned correctly - ?
3. Low Voltage to the water heater - Don't know why this would all of a sudden happen
4. Electric Polarity to unit is incorrect- Don't know why this would all of a sudden happen


I am finishing my basement and have been cutting wood down there. I have tried to keep everything as clean as possible, could the dust have done something?

Thanks and any help would be appreciated. Ice Cold showers suck!


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## liquidplumber

When you cycle the heater does the ignitor glow?


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## Abs777

I haven't watched it. I will check it out when I get home.


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## AllanJ

SOme of these newfangled heaters, particularly those with electronic control and motorized flues, also have an air filter for the combustion air and the filter could need cleaning.

If combustion air is from inside as opposed to a concentric intake/exhaust pipe to the outside, then your carpentry work down there could have made enough dust to clog the filter.


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## Abs777

I found out what it was. It was a dirty Flame sensor. I guess it was thinking that there wasn't a flame \wasn't getting gas and kicking itself off. I unplugged the water heater, pulled the bottom plate off (1 screw, undid the gas line (turn off the gas first), and pulled out the burner assembly. I then took sand paper and cleaned the flame sensor, put everything back together and boom HOT WATER. It was less than 20 minutes and saved me at least $100. The flame sensor looks like this (on the right) if anyone finds this thread in the future.










Thanks for the help.


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## revkev32

*Thanks so much!*

I just had this problem and your suggestion got me back up and running. Had to register just to say thanks!!! God Bless! Thanks ABS777


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## Abs777

Glad I could help and thanks for the shout out.


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## hikermike

Just wanted to post a reply to say this saved my bacon. I just had the exact same issue - removed the burner assembly, cleaned up the sensor and BAM, hot water, working as normal. Thanks!!


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## caufmantr

*Thank You!!*

Ditto here - system kept shutting off and going into 'lockout' mode after 3-4 seconds of burn. A little sandpaper on the sensor and I'm back up and running - very happy wife and daughter (which makes for a very happy me 

Thanks for the info:thumbup::thumbup:


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## Abs777

Glad I could help out.


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## dkrol

*Thank-you ABS777*

I too, had to register just to THANK-YOU!!

I am a female that has had nothing but bad luck lately..(sitting right now getting my air in my car fixed)...

Well not to change my luck I was taking a shower after mowing my 6acres and NO HOT WATER!!:furious: 

My home is only 7 years old...warranty on hot water heater 6 years (haha).

Looked at the LED panel and seen I had a systems lockout problem.
googled it and found your solutions.:thumbup:

Printed off your solution along with your pic. 

Called my son's dad (good think I never raised his child support payments when my son was young):whistling2: and with a little whinnning he came over and fixed it no problemo. 

My finished walkout had flooded a few months ago and they just finished drywallying so the dust probably caused the issue.

Thank-you soooo much!!!:thumbsup:


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## kek722

Another thank you to Abs777. I have a State water heater but same solution. Thanks again.


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## kevgmeta

Wow! Christmas evening and no hot water. Been having this issue but I had been able to just reset the heater and it comes back on after 3 or 4 tries. That would not work tonight. Finally was going to call a tech tomorrow and decided to jump online. Thank god I did. Thank you all for the help. Took out the sensor like the people above and it worked like a charm. Hope I don't jinx it by posting this. God Bless and Merry Chrostmas!


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## wwoody

*Looks like a recurring problem with a fix you can do yourself*

 This worked for me too. The unit would start up, the igniter would glow, the flame would light and then the system would shut down. It recycled about 3 times, then lockout mode. Then maybe after 30-60 minutes it would "try" again.

"Pulling the burner/ignitor/sensor assembly is fairly easy. Turn off gas, unplug unit, loosen/disconnect the gas tube going to the burner (below electronic/thermostat/valve unit) and disconned the wire assembly plug (again located below electonic assembly) then take off 2 nuts located on a metal panel at base of unit thru which the gas tube/ignitor/sensor wires traverse a metal panel. You can now pull the entire unit out and clean it. I suspect care should be taken to not touch the ignitor as it ceramic & fragile. I cleaned the sensor with fine steel wool, vacuumed the burner unit and the chamber within which this whole assembly resides. Then reposition unit and reconnect gas tube and wires to the "electronic control/valve/thermostat. Obviously care should be taken that the gas tube is reconnected properly. Check for leaks (I use an electronic hand held gas leak detector that I got from one of the big box stores for about $30 (I check all gas equipment as a safety measure from time/time)) when the unit is now (hopefully) working. Note gas only goes thru that tube/connection when unit is running.


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## Michael Thomas

I'll add that I just had to do the same at a Takagi tankless water heater which would cycle on and then quit, displaying a "12" error on the installed auxiliary thermostat.


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## boshjales

Thanks so much for the info. This worked perfectly. My wife is very happy that we had to spare a Saturday service call to tech. Saved $$$!!!


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## Maxun

I will try you fix tomorrow my water heater did the same 4 years ago but fix it by him self. so this time I will try your fix thanks for posting this.


Abs777 said:


> I found out what it was. It was a dirty Flame sensor. I guess it was thinking that there wasn't a flame \wasn't getting gas and kicking itself off. I unplugged the water heater, pulled the bottom plate off (1 screw, undid the gas line (turn off the gas first), and pulled out the burner assembly. I then took sand paper and cleaned the flame sensor, put everything back together and boom HOT WATER. It was less than 20 minutes and saved me at least $100. The flame sensor looks like this (on the right) if anyone finds this thread in the future.
> 
> 
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> Thanks for the help.


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## balsuu

*Big thanks*

Water heater had the same problem. System lockout.

cleaned the sensor and vaccummed the unit for the dust. 

Worked like a charm. Big Thanks Again


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## Arlo

Just in time for Christmas...My A.O. Smith Pro Max High Recovery 50 gallon tank, built in March 2008, is not heating water. The pilot is not out. It seems to kick on and off. Water is a balmy (ha) 80 degrees at faucets. My heating contractor has been here and is ordering a gas limiter valve. It won't arrive until the 26th; five days. Would the above instructions work? The plastic dust covers at the bottom of the heater were not very dirty. I haven't pulled any other covers off. My three teenagers are getting ripe. Anyone?


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## topspin64

*Thank You Abs777*

Hope you're still active on this site and just wanted to say thanks. Just finished completing your cleaning steps and "Bam!" Hot water with no successive start-ups and shut-downs. If you were in WI I'd so buy you a drink. Thanks again.


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## Abs777

Glad it was of help...and Thank you!


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## dhamann48623

*Thank you!!!!*

This worked like a charm! We've been fighting with having to reset the water heater for a week until today when it just wouldn't reset. Husband was online looking up new hot water heaters when I found your thread. I had him try it....it's working great. Except now he's mad he can't buy a tankless  Thanks for saving us some $$$


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## willing to try

*more appreciation*

@abs777 - Had same problem. In the years since the original post my ignitor (now ceramic) / sensor looked like this (attached). I removed (two screws total one for access plate one for ignitor/sensor assembly --- did NOT have to disconnect gas lines), cleaned both (maybe a mistake with the ignitor) with 00 steel wool, reinserted and fired up. Hot water now.


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## Toller

I came here for this exact problem! Wouldn't turn on and showed a lockout code. I turned it off and back on and it seems to be fine now.

We had a one minute power outage just before it happened, but that might have been a coincidence.

Should I clean it or leave it alone? (Assuming it stays better...)
If I clean it, with steel wool, sandpaper, vacuum?


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## beenthere

Steel wool for flame sensor. Don't touch the HSI.


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## cobra617

willing to try said:


> @abs777 - Had same problem. In the years since the original post my ignitor (now ceramic) / sensor looked like this (attached). I removed (two screws total one for access plate one for ignitor/sensor assembly --- did NOT have to disconnect gas lines), cleaned both (maybe a mistake with the ignitor) with 00 steel wool, reinserted and fired up. Hot water now.


I have the same ignitor/sensor as this one. I was in a foul mood because this hot water heater has been a pain for a few years. 
I didn't remove the ignitor/sensor. I reached in with a small piece of 2000 grit sandpaper (what I had handy in my toolbox, I was too lazy to go looking for lower grit) and VERY lightly hit the top and bottom of that sensor. (I wasn't sure what I was supposed to sand so I very lightly did both). I only went 2-3 passes as I get nervous working with gas. (Electrical/Plumbing/Carpentry I can handle, but gas makes me nervous)
Put it back together, the unit fired up, ignited and stayed lit. 

My question. Is this good? Or should I replace that ignitor/sensor assembly? 
Also, I might sand it a bit more later on as I wasn't sure what I was supposed to sand and I went so lightly over both the ignitor and sensor that I can't imagine I did much. 

BTW....THANKS!!!!! I was so peeved, and with the issues I've had with this unit, I was just going to bag it and have it replaced.


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## THANKYOU!!!

I also had this EXACT SAME ISSUE!!! Registered just to say thank you and to hopefully help others!

My hotwater tank model = GPSH 50 200

The sequence worked like this...

1. Blower activated...
2. Heating element activated...
3. Gas valve turned on...
4. Flame produced...
5. Flame went out after a few seconds

Thus no hot water for me, my wife, and two little ones.

I figured there must be some type of sensor that was an issue. I'm an IT guy not a HVAC/Plumber so I'm no expert!

The posts above (especially the picture!) showed me where the sensor was. 

He is what I did to fix it.

1. Turned off the gas
2. Turned off the blower motor (there is a toggle switch on it. Just flip it.).
3. Turned off the power to the blower at the breaker
4. Opened the door at the bottom of the tank. You just need to remove 1 screw.
5. Sandpapered the dickens out of that thing in the picture in the post above...
6. Unleashed the vacuum on it...
7. Sandpapered it again for good measure...
8. Unleashed the vacuum again...
9. Put the door back on
10. Turned on the gas
11. Turned on the power to the blower at the breaker
12. Turned on the blower motor

MANY THANKS AGAIN FOR POSTING!!!!


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## supers05

You should'nt use sand paper. It'll cause quick fouling of the sensor. I use a file or steel wool. Otherwise it works until it becomes so fragile that it falls apart.


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## 9918939

9 pm tonight - no hot water. checked online, found this forum- pulled the flame sensor, cleaned it, popped it in and hot water 30 minutes later. thank you Abs777 for the post.


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## eb243204

Another thanks from me!


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## anna.bowen

Another thank you to Abs777. Also I noticed I had some metal and paint on the burner that peeled off inside the water tank. I just used a small brush and got all that stuff of a burner, cleaned the flame sensor with steel wool and now my water heater is back to work!:glasses::biggrin2:


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## Alitto13

Abs777 said:


> I have a 5 year old AO Smith 'GPSH with Hot Surface Ignition' water heater that will not heat water. I will cycle the power and when it comes back on the fan will run for a less than a minute then kick off, then run for less then a minute and kick off, then it goes into System Lockout.
> 
> I checked the manual and it states these could be the issues
> 
> 1. Gas supply is off or too low to operate - gas is on and working to stove and fireplace
> 2. Hot Surface ignitor not positioned correctly - ?
> 3. Low Voltage to the water heater - Don't know why this would all of a sudden happen
> 4. Electric Polarity to unit is incorrect- Don't know why this would all of a sudden happen
> 
> 
> I am finishing my basement and have been cutting wood down there. I have tried to keep everything as clean as possible, could the dust have done something?
> 
> Thanks and any help would be appreciated. Ice Cold showers suc
> 
> 
> It seems to simple to be true, I remember the same thing when I had a problem with my furnace. I have the same Hot water tank, same problem. Just to the right of the ignitor thingy there is a sensor to indicate the flame ignited. It doesn't make sense but if it has a little corrosion it will keep restarting. Take a piece of sand paper or emery cloth and clean it. I tried it on mine and is working perfectly now! Nothing better then a never ending hot shower! 😃😃😃


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## supers05

You should start your own thread. This is an old thread. The flame sensor is probably dirty. You'll have to either clean it or replace it. The HSI/spark electrode is also probably dirty. The HSI is fragile and don't touch it with your fingers.

Does it indicate any error codes? 

Cheers!


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