Coleman Evcon furnace not lighting


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Old 12-20-22, 08:56 AM
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Coleman Evcon furnace not lighting

Working on a Coleman Evcon natural gas furnace in a mobile home not lighting / igniting. The circuit board has an LED flashing once indicating ignition failure. Thinking maybe a bad igniter or something. Any troubleshooting guidance greatly appreciated.



Thinking I need to remove this to get to igniter?
 
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Old 12-20-22, 11:19 AM
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I removed the assembly and think it may be one of these two devices. The heating element doesnt have continuity so expect its the culprit. The other appears to be a spark starter.

 
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Old 12-20-22, 12:20 PM
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That appears to be a Hot Surface Igniter (long "flat" device) in the top picture. It gets hot (cherry red) and ignites the burner. It should have a resistance of 30-75 ohms. If it's open, that's your problem. The smaller, round device is the thermocouple, which lets the unit know that the pilot is lit. If the thermocouple goes bad, the pilot will light as long as the pilot button is depressed, but will go out when it's released.
 

Last edited by Bob14525; 12-20-22 at 01:17 PM.
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Old 12-20-22, 01:22 PM
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Thanks Bob, my local supply house had an igniter so Ill install it and give it a try. Thanks so much for the info!

TF
 
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Old 12-22-22, 07:47 AM
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Replaced the igniter and it started working again for about a day. Its flashing ignition failure code again. Is there a way to test the thermocouple? I probably should have replaced it as well while I had it apart. Ill be diving back in this morning.
 
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Old 12-22-22, 03:52 PM
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It looked like the hot surface igniter was cracked in your original picture.
I have a feeling it is/was ok and you have a control board problem.
You replaced the igniter and got the same problem.
You need to see if the furnace will light and fail or won't light at all.

If you don't see the igniter come on.... you need to check the 120v to it when it should be lighting.
If you don't get that voltage... the board is at fault.
If the burner lights but goes out in a few seconds... you probably have a dirty flame rod.
It's that metal rod with the yellow wire. clean it with a green Scotchbrite pad. It's just a stainless steel rod. It won't go bad unless the ceramic is cracked.

Remember.... those hot surface igniters are as fragile as glass and will crack if you bump them on anything. I'm a pro and have broken them during installation.
 
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Old 12-22-22, 04:47 PM
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I replaced the flame detector with a generic one. It was straight down had to bend it to mimic the original one. We appear to be back in business now. Weve been running a while with no issues. Thanks for all the input!

TF


 
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Old 12-22-22, 06:44 PM
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I replaced the flame detector with a generic one. It was straight down had to bend it to mimic the original one. We appear to be back in business now. Weve been running a while with no issues. Thanks for all the input!

TF



 
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Old 12-22-22, 06:45 PM
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Been running 3 hours now with no issues. Hopefully its good to go!

TF
 
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Old 12-22-22, 06:46 PM
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Looks good. Make sure flame rod is fully engulfed in the flame and it can't touch metal.
The flame must create a bridge between the flame rod and the metal burner.
Clean and keep the old rod for a spare. They don't go bad. I've never had to change one.
 
 

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