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  1. #1
    Join Date
    Jan 2005
    Posts
    447
    I'm having difficulty trouble-shooting a Coleman Evcon furnace with a Robertshaw HS780 ignition control module. Problem is intermittent, first time I arrived to customer's home furnace was running fine. Cycled unit several times but could not duplicate problem. Unit has in-shot burner with HSI. Second time I went out t-stat was calling for heat, ventor motor was running, had 117V from control to ignitor and 117v back to control, but no voltage (24V) from control to valve.Re-set power,ventor motor came on, ignitor came on, but still no voltage to valve, unit locked out again, reset power again this time unit lit up and ran through a complete cycle???? I'm suspecting faulty control but want to eliminate weak ignitor/sensor. My question is how do you correctly check these units for flame sense? is it in series with the ground terminal on the control. I haven't run across many of these units over the years so any advice would be appreciated.Customer has had ignitor changed 3 times in the past 2 years for same type of problem. If it is indeed an ignitor problem why aren't they lasting longer??

  2. #2
    mrssb is offline Waiting Email Confirmation
    Join Date
    Mar 2005
    Posts
    66
    do you happen to have the model# of the furnace? Some of the older coleman furnaces required a special adaptor to pick up the flame current. Are you sure that the flame sensor is not tied to the neutral leg of the control and not the ground? If I remember correctly the flame sensor is read in milivolts dc, not in microamps dc like many of todays modern furnaces. Is this a one burner barrell heat exchanger? If so we had many problems with ignitors, is there a remote flame sensor on this furnace or is it sensed with the ignitor itself?

  3. #3
    Join Date
    Jan 2005
    Posts
    447
    No sorry didn't write down the model # in my journal, but yes it is a one burner barrell he. There is no seperate flame sensor, it is sensed with the ignitor which is why I drawing a blank on how to test for flame sense.

  4. #4
    mrssb is offline Waiting Email Confirmation
    Join Date
    Mar 2005
    Posts
    66
    Go to the Coleman/York supply house and pick up a remote flame sense kit and the new ignition module (all in one kit), and I promise the problem will go away. Not a real difficult installation either. Sorry, used to know the kit number.(the older I get the more I foget) As far as ignitors go these furnace have a history of eating them. I have asked many and they all think it has to do with the furnace temp at the ignitor when it is running. I am not convinced, yet it does make some sense if you think about it. Could it possibly be somebody is actually touching the ignitor during installation, as we all know this decreases their life considerably.

  5. #5
    Join Date
    Jan 2005
    Posts
    447
    Thanks for your responseMRSSB, if you happen to find the part # for the reto-fit sensor/module kit could you post it on here for me . I'll contact a Coleman ? York dealer in the morning. Thanks again.

  6. #6
    Join Date
    May 2005
    Location
    Seabeck, WA
    Posts
    1,870
    As for the "ignitor touching" issue, I have heard both for and against. I am starting to believe that touching a HSI may not hurt it. Go with the ignition module kit.
    Live for yourself and ask no one to live for you.

  7. #7
    Join Date
    Oct 2005
    Location
    sacramento calif.
    Posts
    1,185
    rheem has a remote flame sense kit also,the sensor included needs to be hooked to nuetral<regardless of whether its wht. or blk.>but the problem there is sensing flame "after ignition".if your ignitor heats but you dont get power out to your gas valve you have a bad module.im sure you are aware the gas valve dosent energize until well after the hsi does.i use honeywell #ichs89

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