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Cleaning the flame sensor.

Gas Furnace Won't Start:

Cleaning The Flame Sensor On An Amana Natural Gas Furnace

 
In This Article:
Access covers are removed to reach the furnace flame sensor. The flame sensor is removed and cleaned with emery cloth.
Related Articles:
Skill Level:
2-3 (Basic to Intermediate)
Time Taken:
About 15 Minutes
Author:
Project Date:
December 2010
 
 
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Every two years the Amana GUIC-070 furnace in my house starts acting up. Sometimes, when the thermostat "calls for heat", the burner will ignite and then go out within a few seconds. The ignition control module will try to start the furnace again, and the burner might stay lit for the normal duration. Over a period of a few months the situation degrades to the point where almost every time the furnace tries to start, the flame goes out within 5 seconds.

On this furnace, the problem is the flame sensor... it develops a thin coating of clear or whitish deposits that insulate the sensor from the flame, so the ignition control module doesn't receive the signal that the flame is actually lit. Without that signal, the control module shuts off the gas valve and then tries starting the furnace again. If 3 to 5 attempts don't succeed in lighting the flame, the control module will wait for one hour and then try again. That's an hour where the house has no heat, and if subsequent attempts to light the furnace fail, it can get pretty cold.

But the fix is quick and simple: Remove the flame sensor and clean it with fine sandpaper.

[See Tools and Materials] [Add your comments below the article]

Newer Gas Furnace:


This is the Amana GUIC070 gas-fired forced air furnace in my basement.

The "070" in the furnace model number refers to the heating capacity, which in this case is 70,000 BTU's per hour. But that's a measure of the natural gas input, not the actual heat output. Amana claims that this furnace is 80% efficient, so that results in a heat output of 56,000 BTU's per hour.

That seems like a small furnace, but it actually does a good job of heating my 1,500 square foot house... considering the house has several old drafty windows and measly R-8 fiberglass in the walls.

Amana GUIC-070 forced air gas furnace that fails to start.
 

 

Turning off power to furnace.
Turn Off Power:

Before doing anything, I turned off the power switch on the side of the furnace.

 

 

Remove Access Panel:

Then I removed the upper access panel.

Like many furnaces, this Amana furnace has an upper and lower access cover. The lower cover exposes the blower chamber.

To prevent furnace operation with the lower cover removed, there is a cut-off switch (like the switch that turns on the light in your fridge) behind the lower cover panel.

There is no such switch for the upper access panel, so it is possible to operate the furnace with the cover off. But it's not recommended to run the furnace with the cover removed.

Removing upper access panel on Amana GUIC furnace.
 

 

Warning:

Repairing your own furnace can create dangerous problems such as gas leaks, uncontrolled flames, improper combustion or carbon monoxide poisoning. The author and publisher of this article will not be held liable for any damage or injury caused by attempts to follow the information in this article. If you are not sure of your abilities, or if your furnace is different from the one shown here, then the best course of action is to call a qualified furnace repair technician.

This article should be considered as entertainment, not as instructions. The publisher makes no guarantee of the accuracy or suitability of the information on this page.

 

Amana furnace (model GUIC070) with upper access cover removed.
Furnace Controls:

Behind the upper access panel are most of the components required for the combustion process.

The burner box is at the bottom of the enclosure

 

 

Burner Box:

Using a 1/4" nutdriver, I removed four sheet metal screws that secured the cover to the burner box.

Removing screws for burner box, Amana forced air furnace that won't run.
 

 

Inside view of burner box, Amana forced-draft gas furnace.
Inside The Burner Box:

The cover to the burner box just pulled off, exposing the gas orifices and the burner tubes.

 

 

A Wiring Diagram Helps:

There is a wiring diagram in the owner's manual for the Amana GUIC-070 furnace. The flame sensor is highlighted in yellow.

Note that the schematic shows a single wire, labeled as blue (red arrow) running to the flame sensor.

Wiring schematic for Amana furnace, showing location of flame sensor.
 

 

Location of flame sensor inside burner box on Amana GUIC070 furnace.
Locating The Sensor:

In the burner box there is a device with a single blue wire connected to it. This is the flame sensor.

 

 

Removing The Flame Sensor:

I pulled the wire connector from the end and removed the hex-head screw with a nut driver (red arrow).

Removing flame sensor on Amana GUIC gas forced-air furnace.
 

 

Flame Sensor:
Flame sensor removed from Amana furnace that won't start.

I removed the flame sensor from the burner area.

Removing this sensor was a little tricky because I had to rotate it a certain way to get it out of the hole.

 

 

Close-Up :

Note the white powdery residue on the flame sensor.

This residue needs to be removed.

Close-up view of deposits on flame sensor for Amana residential gas furnace.
 

 

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Cleaning deposits from flame sensor for Amana furnace that won't run.
CLEANING THE FLAME SENSOR:

I used a piece of 400 grit emery cloth to remove the residue from the flame sensor.

 

 

AFTER CLEANING:

Then the sensor was clean and fairly shiny.

Amana furnace flame sensor after cleaning off deposits.
 

 

Replacing flame sensor in Amana furnace that would not start.
RE-INSTALLING THE FLAME SENSOR:

To install the flame sensor in its hole (arrow), I had to insert it as shown and rotate it until the screw holes lined up.

There are some obstructions inside the metal housing, and it's possible to insert the flame sensor into a wrong position where the device cannot be rotated to align the mounting holes.

 

Once I had the flame sensor re-installed, I connected the wire and replaced the cover to the burner box.

I replaced the upper access cover and turned the power on. Since the thermostat was "calling for heat", the furnace began its startup procedure. But this time when the flame ignited, it stayed lit instead of going out after 5 seconds. The furnace functioned properly afterwards. In two more years, I will probably need to clean the sensor again.

More Info:
Tools Used:
  • Nutdriver, 1/4"
Materials Used:
  • Emery Cloth (Sandpaper) 400 Grit
 
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