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A furnace flame sensor works by detecting the presence of a flame within the furnace. As the gas valve opens to begin the combustion process, the current is sent out from the sensor in order to detect the presence of heat from a flame.
How do I know if my furnace flame sensor is bad?
Signs of a bad flame sensor Furnace burners turn on but go out after a few seconds. Soot and other debris is covering the end of the sensor (cleaning the flame sensor may fix this issue rather than a flame sensor replacement) Tip of flame sensor is black. Porcelain/sensor casing is cracked.
What does the flame sensor do on a furnace?
A flame sensor is a crucial safety component on your gas heating system. During the ignition cycle, your gas furnace goes through a process where a spark or a hot surface ignitor will actually ignite the gas. As the gas is ignited, the flame sensor creates a current of electricity.
How does a 1 wire flame sensor work?
The flame sensor when heated up acts like a cathode of the vacuum tube. It emits electrons which flowing to the ground through the flame, like in the vacuum diode.
What does a faulty flame sensor look like?
First, check for your gas burners to light up and then go out after a few seconds. This is the most common sign of a sensor issue. Second, if you can actual see soot covering the tip of the sensor, it’s time for a cleaning. If you look at the tip and it’s black, it’s time for service.
Can you bypass a flame sensor?
Well, while disappointing to some readers, here is the answer: No, bypassing the flame sensor isn’t a solution. You won’t find steps to bypass the flame sensor anywhere. Attempting to bypass the flame sensor is not a good idea, even if it were possible. The flame sensor is an important safety feature on your furnace.
Can you Ohm a flame sensor?
Follow these steps to test the flame sensor: You can do this by powering down the furnace and taking an ohm reading between neutral and the burner assembly/manifold. You should read a few ohms of resistance max, the lower the ohm reading the better grounded it is.
Are flame sensors universal?
Universal flame sensors: You might not need an exact replacement part. Universal sensors are available too. They are available at Home Depot, Menards or other building supply store.
Why does my furnace blower turn on and off constantly?
you most likely have a bad fan limit switch. Your furnace fan limit switch is basically a control system that determines when the furnace blower assembly should turn on and off. So if your furnace blower is turning on and off when the furnace isn’t in a heat cycle, it usually means the fan limit switch is defective.
What is flame sensor made of?
A flame sensor is nothing more than a stainless steel rod partially encased in porcelain. By itself, it does nothing. There are no moving parts, no switches. When attached to a control module, the module sends out an A/C voltage to the sensor.
Does a flame sensor need to be grounded?
A flame sensing rod is a piece of metal with a ceramic insulator that keeps it from grounding out. That is all. However, because it is conducting in the millionths of an amp (microamp), a lot can go wrong with it that a normal electrical component wouldn’t have any issue with.
How much current does a typical flame sensor produce?
The current is very small usually less than 10ua (microamps) 10 millionths of an amp. If the flame sensor gets dirty clean it with steel wool not sandpaper. Any sand residue left behind when heated turns to glass and blocks the current flow.
What are flame rods?
Flame rods are used on process burner pilots to confirm that a flame is present. Flame rods work due to the ionization / rectification process to complete a circuit. When the flame rod is energized the current produces a positive charge that attracts the negative ions in the flame.
How do you bypass the flame sensor on a furnace?
Turn off electrical power to your furnace either at the furnace or at the electrical box. Close the gas valve. Remove the flame sensor.Cleaning the Flame Sensor Shut off power and gas to the furnace. Remove the sensor. Clean away soot and corrosion with a clean emery cloth. Reinstall the flame sensor. Restart the furnace.
Why do flame sensors fail?
What are causes of a dirty flame sensor? As with any piece of equipment a simple reason could be that dirty flame sensor just goes bad. However a more common reason is that it is just dirty. It is a sensitive sensor so any type of dust or carbon buildup could cause it to malfunction.
Are all flame sensors the same?
Not all furnaces have a flame sensor, but if your furnace has one, it will be mounted close to the burner with the metal rod positioned in the flame. Flame sensors vary in size (2 to 4 inches) and shape (see examples below).
How often should you clean your flame sensor on your furnace?
We usually advise that you schedule furnace maintenance every 1-2 years (ideally once a year) and duct cleaning at intervals of 3 to 5 years for a smooth-running system and excellent indoor air quality. That’s the minimum.
How many volts should a flame sensor read?
Now we want to check flame sensor voltage. If the voltage is not within range there will not be enough electrical pressure to push the current through the flame. With your voltmeter, check the voltage between the sensor wire and the burner – it should be 90-107 volts AC.
