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Abs777 04-27-2010 08:08 AM

AO Smith GPSH water heater in System Lockout mode
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!

SuperPlumberGuy 04-27-2010 12:12 PM

When you cycle the heater does the ignitor glow?

Abs777 04-27-2010 12:15 PM

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

AllanJ 04-27-2010 08:27 PM

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.

Abs777 04-28-2010 07:48 AM

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.

revkev32 07-16-2010 07:01 PM

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

Abs777 07-18-2010 06:06 PM

Glad I could help and thanks for the shout out.

hikermike 06-06-2011 06:43 AM

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!!

caufmantr 06-21-2011 09:00 PM

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:

Abs777 06-22-2011 06:22 AM

Glad I could help out.

dkrol 08-02-2011 02:37 PM

Thank-you ABS777
I too, had to register just to THANK-YOU!!

I am a female that has had nothing but bad luck lately:mad:..(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. :eek:

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:

kek722 08-08-2011 08:58 PM

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

kevgmeta 12-25-2011 09:18 PM

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!

wwoody 04-03-2012 10:36 AM

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.

Michael Thomas 04-05-2012 01:08 PM

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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