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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 flame sensor is bad?
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?
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.
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.
What will a bad flame sensor do?
What happens when a flame sensor goes bad? Without a flame sensor, your furnace will keep emitting gas even when there’s nothing to ignite it, resulting in hazardous gas buildup. If your flame sensor is dirty or faulty, it will automatically shut down the heating unit if it doesn’t detect a flame.
How often should a flame sensor be replaced?
Flame sensor lifespan If you’ve just replaced the sensor or had a new furnace installed, you can expect the flame sensor to last for about five years. The average lifespan of a furnace is 15 to 30 years, so you can anticipate a flame sensor replacement once or twice over the course of your homeownership.
How does a gas furnace flame sensor work?
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.
What would cause a gas furnace not to ignite?
The Pilot Light (Faulty Ignition Sensor) The pilot light or ignition sensor is usually the most common issue when your furnace will not ignite. This is typically the problem if you can hear your furnace click on but it does not fire up. If the sensor or ignitor is dirty, it will need to be cleaned.
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.
Will furnace run without flame sensor?
The flame sensor is an important safety feature inside a furnace. Without the flame sensor, if the pilot light goes out but the gas valve remains open, the gas will not burn and will seep out of the furnace. This is a dangerous situation that can result in gas poisoning or even an explosion.
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 is a good flame signal?
When the flame lights, you should read between 0.5 and 10 microamps (μA), depending on the furnace. Readings between 2 and 6 are common.
Is a flame sensor AC or DC?
The mechanics of flame sensing The voltage at the sensor is ac (alternating current), but because of the great difference in mass between the flame sensor and the furnace chassis, this voltage is “rectified” from ac to dc (direct current), usually less than 10 microamps.
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.
Why does my furnace start up and then shut off?
The HVAC filter gets caked with dust and other debris over time. This causes short-cycling as you’ll notice your furnace running for a short while before turning off. The heat will build up, and your furnace will shut down as a safety mechanism. Wash or replace your furnace filters when necessary.
Why does my furnace blower turn on and off constantly?
If your blower is constantly turning on/off when the furnace isn’t heating… you most likely have a bad fan limit switch. 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.
How much is a flame sensor cost?
Flame Sensor If the sensor is bad, it won’t be able to sense heat and will turn the furnace off. The average cost to repair or replace a flame sensor is between $75–$200.
Why do I have to keep cleaning my flame sensor?
It’s possible for a flame sensor to go bad; but more often than not, it is not broken, just dirty from carbon buildup. Because a flame sensor has a very low tolerance for variations in the reading it takes, the slightest coating of carbon can cause it to misread and shut down.
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.
