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Munchkin 926 upgrade gives F13 error

Hello...I am a reasonably handy homeowner with a Munchkin T80M installed in 2004. It has been having trouble detecting flame (F10 error) at random intervals, including when we are out of town, which is a huge problem. I learned that an upgrade to a 926 board would improve the flame sensing reliability by increasing the sensing voltage and using the spark rod as an alternate sensor.

I bought the 926 upgrade board (Munchkin 7250P-731 Control/Display Replacement for 925 Controller) by mail from a supplier to remain nameless. This board is supposed to be programmed for the model of boiler it will go into.

Installation was trivial, but the board gives me an F13 error (fan speed too low). I put the old board back, and it is running without any problem.

Unfortunately the supplier was not helpful...they insist that I must have a fan problem, that I could have damaged the new board, etc., etc.---basically, customer is always wrong. I also wrote to HTP, because they had been very helpful to me with tech support when the boiler was first installed. Unfortunately, they responded telling me that I should hire a contractor.

Back in 2004-06, (which had a different layout then) was also a great source of information and advice! I have not been back for some years.  My question is, what would cause the F13 error with the new board but not the old one? Could the board have been programmed by mistake for a different model with a different fan? (The supplier denies it.) Is there any other possibility and anything to check?

Thank you very much,


  • Nom_DeplumeNom_Deplume Member Posts: 51
    additional info

    I apologize for opening a 2nd account to post additional info. I cannot log into the old account; I asked for a new password twice but did not receive it.

    I wanted to add that the boiler may be 8 years old but it is clean and in great condition.The blower fan runs well with the old controller. It's been tuned up recently with a combustion analyzer.

    Regarding the F10 error, the flame sensor is clean, the electrical connectIons are not loose, and the screws holding the burner assembly down are clean and tight. Unfortunately, the flame current with the old controller fluctuates a lot; sometimes it is 4 (microamps?) but sometimes it goes down below 1.0. It never goes a whole season without a F10 failure. That is why I wanted to upgrade the control board.
  • Steve WhitbeckSteve Whitbeck Member Posts: 669

    F10 is caused by flame failure after ignition not failure for the burner to light. If Your boiler is sitting on the floor then check the drain line for blockage. Also put a level on the blower transfer duct to the front of the heat exchanger. The boiler has to tip slightly backward to stop collection of water in the front of the heat exchanger. Do NOT put the level on the top or front of the boiler case.

    If your boiler is holding water the new style 926 control won't help. Your flame sense should be fairly constant. If it is jumping arround a lot then there is a problem.

    The burner should fire off with a D7 reading ( flame current ) of at least 1.5 and quickly build to at least 3. A clean properly set up boiler will have a 4.0 reading.

    With the 926 control You should see at least 9 micro amps.
  • Nom_DeplumeNom_Deplume Member Posts: 51
    no water

    Thanks for replying! Boiler is not holding water. I vacuum out the coffee grounds and use CLR on it every year.

    Any thoughts on the new board F13 error?
  • ColoradoDaveColoradoDave Member Posts: 54

    I had a F13 error problem on a Munchkin 140m w/ 925 board installed.  It turned out to be as simple as pulling the fan connection and reseating it.

    However, on this particular Munchkin, there was an adapter plug to connect to the fan that newer munchkin's did not have.

    Long story short, make sure the connection lead from the 925 board is making good contact.

    Placing the unit into test mode (S2 & S3 together for 1 second).  The display should alternate between "Ser" & a 3-digit number (number x 10 = fan speed rpm).  If you get a number you can use S1 & S2 to increase/decrease the fan speed between around 134 (1340rpm) & 430 (4300rpm).  If you don't see a number either the connection is bad or the control is bad.  (Assuming the fan is running).
  • ColoradoDaveColoradoDave Member Posts: 54
    Almost forgot!!!

    the "test" mode will clear itself automatically after 10 minutes, or you can press S1/S2 together for 1 second to exit test mode. 
  • Nom_DeplumeNom_Deplume Member Posts: 51
    fixed it

    Many thanks for the reply. It can't be the connection since the error happens with one board but not with the other.

    I haven't been checking this thread since the problem is fixed.  I had the board reprogrammed by a local dealer, and the problem went away.

    One thing I didn't mention here is that the board arrived with a label "R1 140" (my boiler is a T80M).. The vendor said there is no difference! Then, the board gave a "FLu" error; but the T80M has no flue switch. I jumpered the switch, and then got the F13.

    Programming the board correctly cleared all this up.

    I will know not to deal with this vendor again.
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