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AMERICAN STANDARD G-27 HELP

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Hey guys, i have a g 27 american standard heater/boiler thing, I do not know much about this thing at all and its just me and my ol lady that live here. I only recently found out how to manually light the pilot last year. had no issues then. this year ive had to re light the pilot multiple times (not more than once a week) until the last couple days and today it shut off as soon as it was light and turned to on. now i cant get pilot to stay lit. please help.

IMPORTANT SIDE NOTE: So on the instructional plate on this thing it says to "Turn the manuak gas cock valve to off position for 5 minutes before lighting pilot"

I have no idea what that is to do that. please guide me through this!?

20251221_001843.jpg 20251221_001828 (1).jpg 20251221_001717.jpg

Comments

  • mattmia2
    mattmia2 Member Posts: 15,648

    in your case turn the knob on the combination gas valve to off and wait the 5 minutes but those instructions are likely for an old gas train that had a separate gas valve, regulator and manual pilot and main shutoff valves that was replaced with that combinatin valve.

    does the pilot burner envelop the thermocouple, the little copper colored rod well while you have the button/knob held down? most likely the thermocouple is wearing out but if the pilot burner isn't heating it that will also keep it from generating enough current to hold the safety valve open. you are holding the button down for about a minute to heat the thermocouple before releasing it, right?

  • mattmia2
    mattmia2 Member Posts: 15,648

    it could be an issue with gas pressure too. i think you need a good gas tech at this point.

  • beautifullife534
    beautifullife534 Member Posts: 5

    I hold the button down for a few minutes at least. After 1 minute, i start to release it to turn on and if it starts to go out again ill press it back down for awhile. im thinking we need a good gas tech also but cant afford one til after winter. should i try holding it down longer? I use to have a maintenance buddy at Hershey and he came to light it last year and held a torch to it for a lil bit bc he said it needed to warm up the thermocouple or something like that. i just know it had to do with warming something up good enough to stay on.

  • beautifullife534
    beautifullife534 Member Posts: 5

    I can try to take a small video of it soon and post it on here

  • mattmia2
    mattmia2 Member Posts: 15,648

    is the pilot burner heating it well? shouldn't need a torch, the plot burner should heat the thermocouple enough. the real test is to test it with a voltmeter but if the pilot burner is doing a good job of heating the thermocouple then you can try replacing it but your level of skill really seems to be where you should have a pro do it.

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 19,640

    You probably need a new thermocouple. You can get them at some hardware stores, Big Box store maybe and a plumbing/heating supply house for sure.

    maybe your buddy can give you a hand changing it. If the thermocouple is bad not much you can do but change it.

  • beautifullife534
    beautifullife534 Member Posts: 5

    maybe? i do have a voltmeter and i do know how to use it. but ur right, my skill level is not efficient enough with this type of stuff to do anything other than basic troubleshooting.

    if tested with a voltmeter, what would that tell me?

  • beautifullife534
    beautifullife534 Member Posts: 5

    How do i figure out if the thermocouple is bad? Thats probably the only part on this thing other than the pilot and valve that i know what is what.

  • mattmia2
    mattmia2 Member Posts: 15,648

    looks like it should read over 18 mv if you disconnect it and hold the button down to keep the pilot lit. it is a coaxial connection so you read between the center and the outer casing:

    https://digitalassets.resideo.com/damroot/Original/10013/60-2087.pdf

  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 11,588
    edited December 22

    I believe we need to start from scratch with @beautifullife534

    Screenshot 2025-12-21 at 7.30.29 PM.png

    You can use the same valve that you use to light the pilot as the manual valve. It is the same valve you turn to pilot and press down to light the pilot.

    • So the first step is to turn that of OFF and wait 5 minutes to clear any gas from the combustion chamber.
    • Next is to turn the valve to pilot and push down to let gas flow to the pilot burner and light that with a flame.
    • Once the pilot is lit, the thermocouple needs to get hot enough to generate 30 MV (millivolts) of power in order to hold the pilot valve open.
      • The thermocouple has two dissimilar metals inside it that generates electricity when it gets hot.
      • The pilot flame can make it very hot.
      • If the pilot burner is dirty and the pilot flame is too short to engulf the thermocouple in the pilot flame, the metals will not get hot enough to generate enough electricity to keep the pilot burner valve open and it will go right out.
    Screenshot 2025-12-21 at 7.45.12 PM.png
    • Another problem can be that the thermocouple is worn out and no amount of heat will cause it to make enough electricity to keep the pilot valve open

    Here is a link to a regular thermocouple that you can replace Thermocouple

    If you find that the pilot is not large enough to heat up the business end of the thermocouple, then you need to have the pilot burner cleaned.

    If the pilot is big enough to heat up the thermocouple, then your thermocouple is bad and needs to be replaced.

    Hope This Helps

    Mr. Ed

    PS. If you attempt to clean the pilot burner, do not put anything metal inside the tiny pilot burner orifice to open it up. Doing that may damage the orifice and make the hole too big. Using a damaged pilot burner is HAZARDOUS and may cause damage, injury or death.

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

    mattmia2
  • mattmia2
    mattmia2 Member Posts: 15,648

    the thermocouple is just a junction of dissimilar metals that produces a current from the temperature differential at the pilot burner vs the ambient room temp.

    EdTheHeaterMan