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weil mclain ultra 105 series 2 first digit 6

IZZY
IZZY Member Posts: 59
in Gas Heating
Hi, I had this code last heating season. The boiler would start to heat for a few minutes, first digit 3 with the current water temp. After the temp rose a little, first digit went to 6, and then started a new cycle. This sequence would just keep happening (1,3, then 6, and back to 1) and the water temp would only gain maybe 1 degree each time. I did some research and it seemed that the supply/return sensor was bad. I changed the temperature sensor and that seemed to fix the problem.
I just turned the heating system on for the 1st time this season and it did it again, from a cold water temp around 75 and going up to 104, and then I got the 6 again. This time, however, after the heating cycle started again, it ran properly. Any thoughts? Should I expect the sensor to crap out again just to have it on hand in case it does? Since it happened two years in a row, I'm wondering if it might be some other issue causing the part to fail. Any ideas or experience with this?

Comments

  • HVACNUT
    HVACNUT Member Posts: 6,568
    Have you checked and cleaned the igniter/flame sensor?
    When was the last time it was opened up and cleaned inside?
    How's the inhibitor level?
    Just a 6 could be flame failire, as indicated. The right tools will tell you why.
    All sensors can be checked using the ohms chart in the manual. 
    IZZY
  • kcopp
    kcopp Member Posts: 4,514
    May not be an issue.
    If the outdoor temp is higher...say 40F then the system high limit will also be higher. Do you have the outside temp hooked up?
    IZZY
  • IZZY
    IZZY Member Posts: 59
    first off- I apologize for not responding sooner, I thought I would get notified via email when a response came in and have been checking incessantly. I just now thought to log back in and see if there were any responses. 

    kcopp, the outside reset is hooked up, and outdoor temp was above 40, but I got the "6" on initial fire up, and then not afterwards.

    I will run it again once I change the expansion tank. the pressure went way up, just under 30, and don't want to run it until that is in check.

    hvacnut, thank you. I did a complete burner/ heat exchanger clean last year and it worked great all last heating season. I'll see if I can find the sensor ohm rating chart and check that out.

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