AMH950703bxaf cycling

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  #1  
Old 01-31-18, 05:37 PM
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AMH950703bxaf cycling

I've got the above listed furnace, came with the house however no documentation was left behind.
I'm having an issue where it is cycling, described below:

Demand for heat
Small fan turns on and runs for 10-15 seconds
ignition coil glows for some time
gas is released and ignites
flame is sensed (2.2 to 2.8 microamps, after cleaning rod)
ignition coil turns off
after 5-10 seconds of heat, flame is extinguished
small fan turns off after 10-15 seconds
immediately start the process again.

However, the problem is intermittent. Throughout the day, the furnace has been running fine. Now, towards the evening, it appears to be struggling. I first observed the problem over this past week, after having a Nest E smart thermostat installed.

Any thoughts?
 
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  #2  
Old 01-31-18, 05:53 PM
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What is the LED blink code reporting? This is on the controller board that you can see through the plastic portal on the blower section of the furnace.
 
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Old 01-31-18, 06:12 PM
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Last time I observed the LED, it flashed 7 times, indicating an issue with the flame sensor, which is what prompted me to clean and check amperage.
 
  #4  
Old 01-31-18, 06:31 PM
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Welcome to the forums.

I'd say 2.2ua-2.8ua is on the border of acceptable.
Are you sure the rod is completely engulfed in the flame.

Here's the manual for your Amana furnace.... Amana_AMVC_ACVC_ADVC.pdf


On edit:
From page 85 of the manual.....
The Integrated Ignition controls will have 1 to 4 microamps. If the micro-amp reading is less than the minimum specified, check for high resistance wiring connections, sensor to burner gap, dirty flame sensor, or poor grounding.

I'd consider 1ua to be too low for reliability. I'm not sure if 1-4ua is the range for your furnace or if some value is listed elsewhere.
 

Last edited by PJmax; 01-31-18 at 06:47 PM.
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Old 01-31-18, 09:32 PM
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These two photos show the location of the flame rod. the top half of the rod is sitting in the middle of the flame.
 
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Old 02-01-18, 08:57 AM
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Gas or propane? Just guessing - Maybe a supply issue?
 
  #7  
Old 02-02-18, 03:43 PM
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Just following up on this issue.

I went ahead and changed the flame sense rod and took a reading, this time landing between 2.8 and 3.0 uA. I haven't noticed the issue since changing the flame sensor, so I think I will call this issue resolved.

Thanks for the help everyone!
 
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Old 02-02-18, 03:53 PM
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That means your old rod was still dirty or not oriented correctly in the flame.
You can bend the mounting bracket slightly to bring the rod closer to the burner.
 
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