Troubleshooting Guide for Flame Guard and Flame Lock Water Heaters

411 plumb Flame Guard and Flame Lock Gas Water Heaters are made by American Water Heater Company and sold under the names American Proline, Whirlpool, Envirotemp, Mor-Flo, Powerflex, Premier Plus, US Craftmaster and possibly others. The Flame Guard and Flame Lock are names for FVIR (Flammable Vapor Ignition Resistant) Technology designed and manufactured by American Water Heaters. FVIR is a required safety design on gas water heaters that includes a sealed combustion chamber with a flame arresting barrier on the combustion air inlet and a device that detects a taller burner or pilot flame and shuts off the gas supply to the burner. If flammable vapors enter through the flame arresting barrier they may burn as excess fuel in the burner area but the flame cannot flash back through the flame arrestor to the source of the vapors preventing fire and explosion. Older styles of water heaters without the FVIR Technology could be an ignition source for flammable vapors, possibly causing and explosion and fire if a flammable liquid was spilled nearby.

Clogged Flame Arrestor on the Bottom of the Water Heater

Clogged Flame Arrestor on the Bottom of the Water Heater

Burner Enhancement Kit

Burner Enhancement Kit

There are a lot of possible problems with water heaters many of them quite generic which will not be covered in this trouble shooting guide. The focus will be on problems specific to the Flame Guard and Flame Lock design water heaters.

Early models of the Flame Guard and Flame Lock Water Heaters had a specially designed thermocouple that included a one time use thermal fuse that was designed to trip when a taller than normal flame occurred. These thermocouples were unusual in that they had a thermal fuse in addition to the usual flame detection function and they had a left handed thread to prevent the substitution of a regular thermocouple. The availability of these unique thermocouples was limited to a limited supply at Lowes and through American Water Heaters. The poor supply of replacement thermocouples with a fee for shipping and handling from American Water Heaters resulted in a Class Action Suit and Settlement where owners were supplied with a “Enhanced Burner Assembly” which included a new combustion chamber door, pilot/thermocouple assembly, burner assembly, and a thermocouple adapter. The models included in this suit have a round sight glass in the burner door and have serial numbers beginning with “FG” and “FL” and were manufactured between 2000 and 2006. Water heaters manufactured after 2006 have the “Enhanced Burner Assembly” already installed and have a serial number starting with a “B” The Class Action Settlement Period ended June 28, 2008.

Thermocouple Adapter

Thermocouple Adapter

The “Enhanced Burner Assembly” fixed the problem with the one time use thermocouple by using a resettable thermocouple which screwed into a thermocouple adapter. The thermocouple adapter screws into the left hand threads where the original thermally fused thermocouple screwed into the gas valve. Instead there is a reset button in the door of the burner assembly and 2 wires which connect to the thermocouple adapter.

FVIR Reset Button

FVIR Reset Button

The basic problem in most cases is a lack of combustion air caused by the screen of the air inlet on the bottom of the water heater. Frequent cleaning of this screen is required to avoid trouble. When the burner becomes starved for air the flame gets taller just like it would in an FVIR event and causes the sensor to trip. Some of the kits along the way also included a prefilter that wraps around the base of the water heater. If you have one of these keep it clean as well. Many people have luck making up a piece of pipe with an elbow on it to attach on the end of a vacuum cleaner hose to vacuum clean the screen under the water heater.

If cleaning the flame arrestor screen under the unit does not cure the problem there may be other problems relating to draft, insufficient combustion air, negative air pressure in the building or another problem in the unit that is best left to a licensed plumber.

If you have any questions or need additional help please leave a comment and I will reply.

Posted in How To Plumbing Tips, Water Heater Repairs Tagged with: , , , ,
119 comments on “Troubleshooting Guide for Flame Guard and Flame Lock Water Heaters
  1. Matt says:


    I need some feedback. Just installed the new l.p. manifold kit with the thermal reset switch on US Craftsmaster. Everything works as it should however after 2 minutes of running the flame starts to stutter and the burner glows red. Water heater continues to operate fine but I can slightly smell gas. Called the company and they had no suggestions. My old manifold had a cast iron burner this one is sheet metal. Can someone verify that the sheet metal burner operates at a glowing red temperature? Thanks.

    • Redwood says:

      Hi Matt,
      There are many things that could be going on but the #1 concern is you can smell gas.
      I strongly recommend shutting the water heater off and calling a plumbing professional to examine the installation, and diagnose what the problems are with this unit.

  2. Mubbin says:

    Hello Redwood,

    I had a john wood water installed in 2009(model JW40S34FV)which started giving problems in 2012 – pilot light would go off.

    A technician took apart the burner unit which was covered with some brown corrosive liquid. John Wood subsequently replaced the burner unit in 2012.

    Apparently, over the last few weeks (May/Jun. 2013), the pilot light keep going off every second day – I turn on the pilot light and same problem.

    I’m now in a dilemma as I’m not sure whether to get a new water heater or get this one “fixed” John Wood is no longer interested in helping out any further.

    Thanks very much

    • Redwood says:

      Hi Mubbin,
      It sounds like the flue might be be improperly installed and condensate is coming back down on the burner and corroding it.

  3. Bob says:


    I also have a whirl pool water heater and my heater has a cast iron burner, I noticed that I can remove the thermo
    adapter and thermo switch from the new burner kit and install it on my old cast iron one, by drilling a hole
    for the switch. I believe it should work, also replacing the thermo coupler with a universal one. will this work ?

    • Redwood says:

      Hi Bob,
      Install the complete enhanced burner kit without modification. The thermocouple adapter also has to be used as the old style thermocouple with the thermal fuse is left hand thread.

      • Bob says:

        Hi Redwood

        Well I noticed that the new unit has a right hand thread thermocouple, which I transfered to the cast iron burner and I used the thermocouple adapter, the only difference is the thermoswitch. I only have to transfer this to my cast iron fron face plate to exactly position like the new one. The only difference is that now you have a heavy duty cast iron unit to the cheap thin sheet metal one. I have finished the transfer but I have not yet drilled the hole to transfer the thermoswitch. That is the only piece I need to install. They are both identical except one is cast iron and the other cheap thin metal but with the thermal switch and thermocouple adapter to fit the right hand thread thermocouple.

        • Redwood says:

          Hi Bob,
          Sorry for legal and liability reasons I cannot recommend or, endorse altering the factory supplied parts of a gas appliance.

  4. Dan in NJ says:

    Great website and need some help please!

    I have Whirlpool and the pilot light goes on but the main burner just wont kick start – I shut the gas off, wait 20 seconds and hold the trip/reset button on the FVIR and that usually works. However, the last few days it hasn’t ignited. I’m trying everything here, do I need a hole new burner kit?

    • Redwood says:

      Hi Dan,
      The “Enhanced Burner Kit” changed the “One Time Thermal Fuse” in the thermocouple to the FVIR button switch. You have the newer version in your water heater.

      Is the pilot light remaining lit but the main burner doesn’t come on or, is the pilot light going out?


  5. Chris Grier says:

    I called whirlpool to get the “Enhanced Burner Kit” but since my water heater was made in 2002(out of warranty) they are charging me $40 and another $20 to overnight it :(

    • Redwood says:

      Hi Chris,
      Sorry to hear that you have to pay for their screw up, unfortunately Class Action Lawsuits do have limitations and eventually the customer’s rights for compensation expire. With an 11 year old water heater approaching the end of its expected service life I’d consider replacement as an option before spending too much money on repairs. With that I’ll give you a strong recommendation for a Bradford White water heater.

  6. Kevin says:

    Hi Redwood,
    Interesting situation. Whirlpool BFG 40 gal propane water heater. Light pilot, thermocouple holds and pilot stays lit. Turn gas nob, and burner turns on. Next morning pilot is out causing to re-light. This has been going on for a few days. Taking a shower requires a trip to the water heater.

    Thought there was a bad draft, but everything checked out and was drawing correctly (and has in the past). Changed thermocouple thinking it may be getting weak after a while. Pilot flame was large, blue, engulfing thermo end, and holding as was before. Still same results – extinguished after one recovery cycle. No vapors or distillates in the area, and thinking it could be a combustion issue, I opened the inner door slightly to allow air in and a clearer look at the burner/pilot. Even recorded a video so I can view time-lapse. Pilot lights and stays lit initially, burner ignites as expected, thermostat reaches temperature, burner shuts off, pilot remains lit for almost 1 minute. Video recorded a slight “twang” similar to a guitar string (not the magnet when thermostat reaches temperature), and the pilot cuts out. Subsequent attempts to re-light pilot fails unless you wait a spell. Thermal switch seems like it kicked in.

    However, there are:

    • a) no flammable vapors
    • b) combustion chamber is open to air now so should not be restricted (will check flame-guard vent anyway)
    • c) thermostat remains on until thermostat has reached temp AND THEN pilot goes out a minute later, not all at once as I would expect if combustion chamber overheated.
    • d) Thermostat for Water temp is set to 120-130 only.

    Water heater is located in well ventilated area and same reaction is obtained whether flame door is on secure or loosened enough to view flames of burner/pilot. Before taking video, was thinking the burner cutting out and having one last backdraft (as gas gets cut from thermostat control) was blowing pilot out (sim to the effect you get w/ an old gas grill), but video proves otherwise. Any thoughts as to what could be happening here?

    • Redwood says:

      Hi Kevin,
      The draft test was an excellent starting point. Did you perform that test while any equipment that moves air in the home was operating? furnaces, dryers, exhaust fans are all possibilities, and the open door does kind of rule out the flame arrestor as the culprit at least while it is open.

      I’d look to making sure the gas pressure is adequate again while the water heater is operating and other gas appliances are also on and operating. If the gas pressure is good then I’d say it is the gas valve that is causing the problem.

      I’ll E-mail you a Troubleshooting Chart PDF File.

      Hope this helps,

  7. bob says:

    I have a gas 50k btu american water heater, powerflex that i recently purchased. It worked fine for about 2 weeks, now it won’t ignite.
    Received the lockout code when it failed.
    The powervent runs, the thermocoupler glows, I hear it switch to push gas through, but nothing happens, no flame, nothing.
    I don’t see a screen (flame arrestor) in the bottom of the water heater.
    Lockout code says,
    1. Gas supply is off or too low to operate.
    2. Hot surface ignitor not positioned correctly.
    3. Low voltage to the water heater.
    4. Electric ploarity to unit is incorrect – test and correct.

    I’ve pretty much ruled out 1, 3, and 4.
    How do I know if the hot surface ignitor is positioned correctly?

    • Redwood says:

      Hi Bob,
      It’s hard to say for sure without being there. Even your ruling out can be suspect, without knowing what you did to rule them out. Did you actually measure the gas pressure? Is it the gas valve you hear clicking? Do you hear gas rushing to the burner? Is gas going to the burner? I’d suggest calling American Water Heater’s Help Line as you’ll need to call them anyway for warranty parts if needed anyhow. They are the ones you’ll have to jump through the hoops for.

      I hope this helps you get hot water again,

  8. Chuuter says:

    Thanks for this article – you are a Godsend! I feel like I at least am headed in the right direction. I have been without hot water since coming back from NY state where I was visiting my family. I got back here the 29th of December. I have a PremierPlus Water Heater that starts with an FG in the serial number. My house was finished and I closed in January of 2006 – probably before the suit was finished.

    I have replaced thermocouples before in the other homes that I have had. It has never been much of a hassle. This one is a nightmare! I have been looking all over the place and reading everything trying to find out why I cannot get a thermocouple for this unit. Should the builder have had this fixed? A bunch of my neighbors in this development all have the same heater model.

    The builder is Sunrise Homes down here in Hillsborough County. Should I try to get the builder to replace this or do I not have a right to ask this since there was a class action suit? If I have no such recourse, what is the cheapest way to get out of this mess? I never thought that a simple thermocouple would turn out to be such a hassle.

    These cold showers are getting old! Can I ask the HOA to put a link to your article on this developments website? If I can prevent everyone else from going through what I am going through this all will be worth it.

    Any help or advice that you could give me would be highly appreciated.

    • Redwood says:

      Hi Chuuter,
      The limitations of the class action lawsuit only includes the water heater manufacturer providing the “Burner Enhancement Kit” without any provisions for installation of the kit with instructions that say, “It is so easy a cave man can do it.” That said, basically the job entails disconnecting the gas supply to the pilot and main burner, disconnecting the thermocouple, and removing all of the screws from the sealed burner chamber door. Once that is accomplished, the entire burner assembly is removed from the water heater. The flame arrestor should then have compressed air blown through it from inside the burner chamber to clean it and allow enough air to flow into the burner chamber. At a minimum the flame arrestor should be cleaned from below with a brush and some attachment on a vacuum cleaner which is slim and curves upward allowing you to vacuum off the accumulated dust and lint on the flame arrestor. Then you would have to install the enhanced burner kit and put all the screws back in while hooking up the gas and thermocouple connections.

      I hardly think that this is a job which should have been left to the consumer, with them being told, “It is so easy a cave man can do it.” but alas when there is a class action lawsuit it never really is a “Win” for the consumer, it all too often is a “Win” for the manufacturer of the defective product.

      What I would recommend is that since you are without hot water that you immediately call State Industries the maker of Premier Water Heaters at 1-800-365-8170 and make arrangements to have them send the “Burner Enhancement Kit” to you, so that you can have hot water again. Then you should get with your HOA and see if you can interest them in helping all of the other home owners in your HOA with finding how many of them have water heaters affected with this defect then perhaps having a plumbing company come in and repair all of them as a group purchase to obtain better pricing. If a company comes in and does the work going from home to home making the repair they can do the work more efficiently and pass the savings on to the HOA as a group.

      You are certainly welcome to link my website on the HOA association website to provide this information to the other homeowners and help them out with their water heater problems.

      I hope this helps,

  9. Brian says:

    I bought a house 2 months ago. I began having problems with the pilot light not staying lit yesterday. Thanks for your site and the information you have provided. I called the company this morning and he said that the previous owner of the house had already ordered the kit (and we are assuming had it installed) and that I should only need to replace the thermocouple. I asked for a part number. He gave it but said that if the kit has been installed that it’s no longer a left-hand threaded deal and I could use any 24 inch thermocouple. Is this accurate? From what I had read here and elsewhere, I don’t remember anything saying that you could use a regular thermocouple after the replacement kit. Please advise. Thanks!

    • Redwood says:

      Hi Brian,
      If the “Burner Enhancement Kit” has been installed you will see that there is a thermal reset button on the sealed combustion chamber door and the thermocouple will have a regular thread rather than a reverse thread. There is an thermocouple adapter that was part of the kit which takes the thermal fuse out of the thermocouple and converts the thread direction as well as taking out the wiring for the thermal reset button to be used. If you have the thermal reset button, and wires from it connecting to the adapter at the gas valve a conventional thermocouple can be used.
      Hope this helps,

  10. don says:

    i have a us craftmaster lpg water heater and after i light it the light flashes 4 times meaning tempature exceded. the pilot light is really big and it does not fire up the burner.

    • Redwood says:

      Hi Don,
      I would recommend calling a plumber to look at your water heater especially if you have already cleaned the flame arrestor. While a clogged flame arrestor and the associated bad draft may cause the flame to bloat, I think your problem may be more serious, especially if you are getting the overheating code flashing.

      The problem may be excessive gas pressure or, the orifice size may be too large, a plumber would have the correct test instruments to diagnose the problem.

      Hope this helps,

  11. Josh says:

    Just wondering if you can help me. My dog somehow chewed off just my thermal switch on my us craftmaster water heater, just wondering If I can just replace that little thermal switch or do I have to buy a new assembly? Thanks

  12. vinnie says:

    Had a power outage an now status light will not come on. no status light then can’t start procedure to light up water heater.

  13. Mike says:

    Hi, I have one of these horrible American Water Heater company/Whirlpool water Heaters that are of the FG model. I already received the replacement manifold about 4 years ago and have now just started having problems again. I noticed the pilot light was out so I went to relight it and it lit right up. The next morning, it was out again. Was able to relight again, but next morning it was out again and this time wasn’t able to relight. Replaced the thermocouple and still didn’t stay lit. Replaced the thermocouple again….still had the same problem. I cleaned the burner with a wire brush and made sure nothing was blocking the pilot orfice.
    I do not not what to do next. I admit I did not clean out the bottom filter, and I will surely do that next. But what would you suggest if that doesn’t fix the problem? Thanks for your help.

    • Redwood says:

      Hi Mike,
      I’d always start with making sure the bottom “Filter” or, flame arrestor is clean so the air flow into the burner chamber is good. However, typically the button on the thermal switch would trip if the flame arrestor was blocked. I’d make sure the Thermocouple is properly positioned in the flame and the pilot flame is good, then test the thermocouple to make sure the voltage from the thermocouple is correct.

      Flameguard Thermocouple

      You can download a copy of of the Flame Guard FVIR Troubleshooting Guide by Clicking Here, and it shows how to test the thermocouple for the 12 millivolts minimum required to hold open the gas valve. If the voltage from the thermocouple is good I’m afraid that the next step would be to replace the gas valve, which is getting a little pricey.

      On the bright side you have an aging Flame Guard Water Heater and the day is approaching where it will need replacing. Have you seen the article here on 411plumb “Bradford White Defender FVIR System Water Heater Review?”

      Hopefully you have a few less hassles with your next water heater,

  14. Rowan says:

    Hi there! I am renting a house with an American Proline Flame Guard water heater, and I’m having some issues. The pilot went out yesterday and now that I’ve relit it, the red status light is blinking four times rapidly. It says that means that it’s overheated, but now there’s no hot water at all (even with the pilot lit) and the status light is blinking four times. I’ve tried to reset it multiple times, and there’s still no hot water. Is there a way for me to fix this? I’m not a very handy person, and I don’t have a lot of money to spend on replacement parts. Any fix you can think of would be appreciated. Thanks. :)

    • Redwood says:

      Hi Rowan,
      You really need to call your landlord on this problem. It is their plumbing and their responsibility to repair it. You could incur liabilities for touching the plumbing beyond normal usage.

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