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I recently have noticed that the flames in my Amana HE furnace has went from the sharp blue flame in the burners to a less sharp, blue and orange flame. It is not to the point yet where it has tripped the rollout sensor, but I can see that a good part of the flame is not making it into the heat exchanger and dancing in front of it somewhat. I removed the burners and cleaned them, they weren't really dirty just a slight rust on the holes which brushed off. There is no blockage in any of the 3 gas orifices. The inducer fan runs fine and exhaust is vented as well as the intake. I even did a test where I held a long match into the heat exchanger and ran just the blower fan to see if air was being introduced, the flame did not seem to move. I'm sort of stumped. Anything else I can check before calling a technician to look? It's an Amana Air command 90 furnace, circa 2000 model.

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    Orange/yellow flame is usually a sign that the gas/air ratio is off. This also produces more CO which can be deadly. Make sure you have a working CO detector in the house. This is very important, families have been found dead in their beds because of this.
    – crip659
    Commented Dec 21, 2023 at 23:06
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    I've moved my CO monitor to right next to the furnace after I noticed the issue, then for days in front of different registers around the house, its never went off once. I also tried adjusting the gas pressure screw slightly while watching the flame, I never noticed a change, but I also don't have a manometer so I don't want to mess with it much. But I'm wondering why the gas mixture would suddenly be off if I've never touched it before this.
    – BigLake
    Commented Dec 21, 2023 at 23:12
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    Dirt or a clog in one(or more) of the tubes. The ends of the intake/exhaust might be clean, but close to the burners can be different.
    – crip659
    Commented Dec 21, 2023 at 23:29

2 Answers 2

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Have you checked the air intake that feeds the burners? If that is clogged in fluff, it will cause the flame to burn more yellow.

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  • Yes the exhaust and intake are clean and unobstructed.
    – BigLake
    Commented Dec 21, 2023 at 23:13
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I'm going out on a limb here. They say, "Hear hoofbeats: think horses, not zebras." So here's a zebra for you.

You live in Michigan. There has been snow recently in the lower peninsula. You live within shouting distance of an active highway or an interstate. Road crews have been spreading salt or brine on the highways to melt snow and prevent ice. Cars drive over the wet, salted roads at high speed and create a mist. The prevailing wind is blowing the mist in the direction of your house.

The mist evaporates and leaves tiny crystals of salt suspended in air. Your furnace sucks in the outside air for combustion, and the salt crystals in the air become ionized in the flame and add an orange color.

Before the guffaws begin, I've seen this happen on the gas flame of a kitchen stove when someone uses a "cool mist" ultrasonic humidifier that has been filled with softened tap water containing sodium which has been exchanged in the softener for calcium and magnesium. You get an intense orange flame instead of blue. There has been at least one post on this Stack about this effect.

So consider the possibility that you're seeing orange sodium light in your furnace flame from microscopic salt particles in the outdoor air.

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  • That's a sensible thought but I actually have my intake inside with a light dust filter on the end.
    – BigLake
    Commented Dec 22, 2023 at 0:10
  • @BigLake "The exhaust is vented as well as the intake." Figured that meant outdoors. So are you using a humidifier with softened water? Same effect, different source for the sodium.
    – MTA
    Commented Dec 22, 2023 at 1:55
  • No water softener, and I still don't think that would cause the weaker flame. It's almost like it's restricted somehow but I don't see where. I'm thinking about pulling the inducer motor and seeing if there's something built up, tho I don't expect to see anything since it's draining water from the exhaust as usual.
    – BigLake
    Commented Dec 22, 2023 at 3:04

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