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Hello forum. I have a Carrier upflow gas furnace, model 398AAZ036060. If this furnace has a flame sensor, can someone please tell me where it is located? I searched the burner compartment but only see the pilot burner and spark electrode assembly near the burners. Thank you for your assistance.
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flame detector
if you look at the pilot burner, there should be three projections on the bracket.
one is the spark igniter, one is the pilot valve thermocouple and one is the flamerod.
the sparker completes its circuit to any known ground within the flame path, the thermocouple generates a millivolt signal to keep the pilot flame going, the flamerod detects the flame presence. -
furnace
watch this you tube video. there's other videos on this page which should help you determine your problem area.
Anatomy Of Hot Surface Ignition: Carrier WeatherMaker 8000 - YouTubeComment
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Thank you for responding. I searched for a glow plug but none existed in the burner area. Also, I further inspected the ignition burner assembly for a third item, a possible flame sensor, and did not see a third item. I provided photos showing what is near the burners. The reason I am looking for a flame sensor is the burners cycle on and off continuously. A pilot flame appears, then jets of flames appear but only briefly. This cycle continues. Additional assistance would be appreciated.
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furnace
I looked at your photos. why is the molex plug disconnected?
your 4th photo shows a spark gap and an insulated flame detector.
I didn't see the standing pilot but I'm betting that 1/4" aluminum pipe that goes into the burner area is it.
another thing that baffles me is the spark gap. normally there's a high voltage lead connected to it, almost orange or red in color. I did not see this.
the short cycling is evident in the second video that explains the flame rod detector.
what happens when you plug the molex together?Comment
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The orange wire broke away from the spark electrode when I removed the assembly. I will try to figure out how to attach it to the end with the screw inside the white plastic. Also, I removed the connector to be able to twist the ignitor burner away from its gas supply line. There is a flame sensor on the assembly? What does the insulated flame sensor look like? The silver gas line attaches to the middle part and the spark electrode encased in the white, square and about two-inch long plastic piece is attached to the pilot burner, but I don't understand what part the flame sensor is. Please describe it. I thought the flame sensor has a thin, metal projection like the spark electrode does. Thank you for continued, helpful responses.Comment
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When everything was connected and properly in place the pilot flame would light and about 45 seconds later the jets of flame would appear, but only for 5 seconds. The burners would not stay lit. This cycle would continue. The pictures show what the furnace looks like now after I removed parts and disconnected the molex plug in an attempt to find a flame sensor. I wanted to clean a flame sensor thinking that buildup on the metal was causing the burners to not stay lit.Comment
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flame rod
if you'd look into the vids I presented, the flame rod, flame sensor is just a piece of stainless steel wire with a coating on it. it is in the flame path.
a dirty flame rod is enough to shut down the burner.
the way it works is, with no flame, there is a 120 volt current on it. this is AC or alternating current.
when there is a flame, this wire ionizes the air so the air conducts electricity but it is now a DC potential.
this DC is picked up by the electronics and keeps the main valve open.
any loss of flame, even spurts of flame is enough to shut down the furnace.
try to reconnect the high voltage wire to the spark gap and clean off that bent piece of wire near the spark gap.Comment
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furnace
did a little more searching.
go to this site:
www dot furnaceparts dot com
left panel look for Carrier
sub-set "Night and Day"
Page #1 about 2/3ds down the page you'll find your 3 wire pilot assembly.
#LH80005
up on the page is the flame rod assembly. this you'll have to look for on your burner.
it's the only thing with one wire on it.
trace the wire back from your control board. it should be marked.Comment
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I have been looking for the flame sensor or glow plug, but nothing exists in the burner area with the description you provided. I don't see a glow plug nor do I see a metal rod sticking into the flames other than the electrode of the spark ignitor portion. Is the flame sensor a contiguous part of the ignition burner? Below the gas port of the ignitor where the 3 wires connect to the ignitor assembly is a white button at the end of the metal strip, which is all connected as a part of the assembly I am holding in the photo. The electrode of the spark portion is different from a metal rod of a flame sensor, or are they the same thing?Comment
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398aaz
When the flame comes on, does the pilot flame stay on? There is a chance the pilot flame is not as strong as it should be. If you lose the pilot you will lose the flame as well. Be sure the area around the pilot is clean of dust and lint.
TomComment
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furnace
did you even look at the site I provided?Comment
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I looked at the site and saw the flame sensor and ignitor burner. I searched everywhere for something that looks similar to that flame sensor, but I don't see any flame sensor. I tried to trace single wires from the control board also. There is no marking on the board for a flame sensor.
A pilot flame appears strong. Now, only a pilot flame appears and not even jets of flames appear anymore.Comment
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I removed any scale and all debris in the burner compartment. Also, I used light sandpaper to clean the electrode on the pilot assembly.Comment
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furnace
locate and send me a picture of the wiring diagram [schematic]
there has to be markings on the control board as to what goes where.
it is very difficult for me to troubleshoot YOUR unit as I am not there to actually see it, so I have to go by a diagram.Comment
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