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Munchkin F18 error after new parts

mopar Member Posts: 1
10 year old Munchkin 140 boiler.  Maintained/cleaned yearly.  Recently have been getting F18 error "gas valve failure"  Replaced gas valve low voltage wiring harness also replaced the gas valve with a new Dungs valve.  Harness is tight to gas valve as are all connections.  Worked fine for 8 days.  Back to F18 error early this morning.  Before new parts were installed was having daily F18 errors usually in the early morning (12-5am).  What's next, a new control board?  Have the 925 controller.  Gas company checked the meter and regulator which are fine.


  • Jamie Hall
    Jamie Hall Member Posts: 17,036
    The thought which crosses my mind

    and, mind you I do not know that much about either Munchkins or gas in general -- is that there have been real problems with gas pressure lately, and I wonder if that particular error message could be triggered by low pressure on the supply side of the valve.

    Which the gas company might well not have found -- the problem might not even have been there when they came around to check.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • MunckinHomeowner
    MunckinHomeowner Member Posts: 1
    Mopar, how did you end up resolving? My munchkin boiler is experiencing the same issues. Thanks.
  • guiher
    guiher Member Posts: 2
    I have a Munchkin I personally installed in 2004, been going strong ever since. Except for the last approx. year I have had the F18 error code problem, and reset the boiler every morning plus. I have cleaned the boiler yearly, I recently replaced the intake air sensor, seemed to fix the problem for a while - now back to the same issue???
    I would really like to know how to solve this?
    Since the boiler worked for 10plus years with out issue, I don't think it can be classified as an installation problem.
    Anybody know how to fix? I checked all connections on the gas valve, and even installed a new wiring harness to no avail?
  • Jr_12
    Jr_12 Member Posts: 38
    Pull up the black plug on gas valve and test the two outside pins(it has to remain in contact with the pins) you should have 18-27vDC. If you don't have have the proper voltage I would trace the wires back to the boards(blue and brown) and test on the backside of the molex for 18-27v AC. If the voltage isnt there it's pointing at a bad control. I have had a couple bad safeties like the water pressure switch or eco draw voltage down enough to cause the issue, but it is extremely rare.
    If you had the voltage going to the gas valve plug it would point towards a bad gas valve.
  • hot_rod
    hot_rod Member Posts: 15,014

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • hot_rod
    hot_rod Member Posts: 15,014

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • guiher
    guiher Member Posts: 2
    I tested this with my meter I got 21.3 VDC, but only when the boiler is actually firing. No voltage when not firing.
    What does this mean? Thoughts?
    Will wait and see if boiler goes into F18 code overnight that is when it mostly happens.
  • j a_2
    j a_2 Member Posts: 1,796
    What is the inlet gas pressure, both static and dynamic...Have you added any gas appliances as of late? Are you in a high or low pressure area....?
  • wzager
    wzager Member Posts: 1
    My 10 year old Munchkin 140 has the 'F18' error code. The issue, I am told, is that i need a software update.
  • clammy
    clammy Member Posts: 2,666
    Its been a while but i had a issue simalar w a f18 code it ended up tracing it to the manual reset temp limit ,it had a bad connection and would code F18 .Check for any moisture on that flue temp sensor it was a booger to find and even though i ordered the hariness i never used it and that was 2 years ago on a then 10 year old m80 peace and good luck clammy
    R.A. Calmbacher L.L.C. HVAC
    NJ Master HVAC Lic.
    Mahwah, NJ
    Specializing in steam and hydronic heating