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Old 05-13-2014, 08:17 PM   #1
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Suburban furnace at high altitude

I have a 2014 Roo 183 that came with a Suburban furnace, possible model number of NT20S.

This past weekend we camped at 8000ft in CO, and the furnace fan would run, but no spark or heat. Long story short, we narrowed it down to this: The thin air will cause the furnace to "think" there's not enough airflow, and thus will not light.

Who else has had this issue? How'd you fix it? I was thinking of putting a small 1" hole in the front panel with a cap of some sort. Then I could pull the cap if this happens again, allowing some increased airflow.

Thoughts?
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Old 05-13-2014, 08:29 PM   #2
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Originally Posted by EricInColorado View Post
I have a 2014 Roo 183 that came with a Suburban furnace, possible model number of NT20S.

This past weekend we camped at 8000ft in CO, and the furnace fan would run, but no spark or heat. Long story short, we narrowed it down to this: The thin air will cause the furnace to "think" there's not enough airflow, and thus will not light.

Who else has had this issue? How'd you fix it? I was thinking of putting a small 1" hole in the front panel with a cap of some sort. Then I could pull the cap if this happens again, allowing some increased airflow.

Thoughts?
I have had no problems igniting with stock set up in Breckenridge (9200) or south park (around 10000) so don't know about your analysis. the air flow device is a sail switch that is not all that sensitive. Donno what the issue might be.
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Old 05-13-2014, 09:38 PM   #3
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garbonz - We figured it was a sail switch issue because the furnace would run just fine with the front panel removed or cracked open for more airflow. I guess mine is an uncommonly sensitive delicate flower.
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Old 05-14-2014, 09:25 AM   #4
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Do you have an obstruction someplace in the air flow? Seems odd that it is that delicate. Maybe try a new sail switch, or do what I do which is to leave it alone if it is working. Sail switches have been known to stick a bit or become intermittent and that is no fun to diagnose. I had that happen on a furnace in a Born Free motorhome years ago and I felt like I was chasing ghosts.
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Old 05-14-2014, 10:14 AM   #5
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I'll check the output tubes to look for an obstruction. I was just running wires down there and didn't see anything, but I'll look again.
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Old 05-15-2014, 08:51 AM   #6
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Has nothing to do with "thin" air". The sail switch is a piece of tin that is in the air flow to the burner. If it works with the cover cracked it is more than likely an obstruction in the inlet air flow.
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Old 05-15-2014, 10:54 AM   #7
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Never had a problem with our furnace. Camped up to 9000 feet last fall and was at 7500 early last week.
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Old 05-16-2014, 10:24 AM   #8
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Has nothing to do with "thin" air". The sail switch is a piece of tin that is in the air flow to the burner. If it works with the cover cracked it is more than likely an obstruction in the inlet air flow.
I wonder if I can adjust the sail switch? Anybody tried that?
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Old 05-16-2014, 01:38 PM   #9
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I don't think there is an adjustment on the sail switch.

I appears that your fan is running but not pushing enough air to actuate the switch with the cover on. So either the sail switch is not moving enough for some reason or there is reduced intake air flow limiting how much air the fan ca produce.

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Old 05-17-2014, 09:18 PM   #10
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you could tape a piece of cardboard to the "sail" to make it more responsive, but the best idea is to replace it if it is acting up. Control boards which recieve the signal from the sail switch could also be a candidate
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