Table of Contents
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 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.
How do you test a flame sensor signal?
You can measure flame signal by putting your meter (capable of measuring micro amps) in line between the flame sensor and the wire that was connected to it (see picture). If you are reading anything under 5 uA (micro amps), it is likely that your flame sensor is dirty.
How do you test a flame sensor voltage?
Now we want to check flame sensor voltage. With your voltmeter, check the voltage between the sensor wire and the burner – it should be 90-107 volts AC. If the voltage is low at the sensor disconnect the molex plug from the circuit board and check the voltage at the corresponding pin on the board.
What is the minimum acceptable reading for a flame sensor?
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.
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.
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.
What setting should the multimeter be on when testing the flame sensing circuit?
Remove the lead from the flame sensor and connect it to one probe from the meter. Then, connect the other meter probe to the sensor terminal. Turn up the thermostat to call for heat and check the meter reading when the burners ignite. It should read between 5 and 10 µA.
How do furnace flame sensors 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.
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 does flame detection electrode work?
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. This produces the direct current signal that is used to indicate the presence of flame.
What causes a gas furnace not to ignite?
Common types of natural gas issues include gas leaks, blocked gas lines, and malfunctioning gas valves. If the gas line is off, simply turn it back on. If the furnace won’t ignite after doing this, call an HVAC professional to check for other potential problems.
What causes a dirty flame sensor?
It is a sensitive sensor so any type of dust or carbon buildup could cause it to malfunction. Most people have their furnaces in a basement or laundry area where there is excess dust in the air. This dust could stick to the sensor making it dirty and causing your furnace to shut down.
How many micro amps does a flame sensor have?
You need to have >1.0 micro amps for the furnace to continue its cycle. Less than 1.0 micro amp and the furnace will shut down and try to recycle.
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.
Why is my flame sensor not working?
A flame sensor failure is pretty common due to buildup of materials and particles in the confined area of the furnace. To clean the flame sensor, start by making sure your furnace is off—it can be turned off using the switch on the unit or by cutting the power source at the breaker box.
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.
