How to clean a dirty flame sensor - Heating & Cooling

The four flashes is failure of ignition. It could be the flame sensor dirty. The furnace tries to light four times before you get the four flashes. The board then locks out for one hour unless the power is removed and restored. You could try gently cleaning the flame sensor with fine steel wool. If you don't have fine wool you can use a crisp dollar bill.
with the burner firing the yellow flame sense indicator should be pretty much locked on or flicker briefly. If it just occasionally flashes on then the flame sensor rod needs to be cleaned.
hope this helps you.

A flashing yellow light means poor flame sensing. This is usually caused by the flame sensor being dirty and/ or the burner being rus ty or corroded. Remove the flame sensor, located opposite of the ignitor, and clean with sand paper or steel wool. If this does not fix the problem the burners may need to be cleaned. I recommend a trained HVAC person do this. This is a picture of a flame sensor
Hope this helps.
Bob

it sounds like the flame sensor is dirty or faulty. when the pilot lights the flame sensor rod recognises the flame to allow the main gas valve to open and ignite the burners. you can clean the flame sensor with some steel wool or sandcloth

If this is for your furnace your flame sensor is probably dirty. Your flame sensor is a rod that sits on the end of your burners to make sure all furnace jets fire if it is dirty it will cycle offf and on fore 3 or 4 tries then lock itself out. what you will need to do is use a piece of sand paper or steel wool and clean the flame rod sensor but be careful because the end of the flame sensor is porcelin and breaks easily. If this help please rate me and do a testimonial.

flame sensor is dirty. steel rod that is in the burners flame path can be removed with 1 screw and cleaned with sandpaper.

Could be a dirty or faulty ignition sensor. This is the sensor that tells the heater that there is a flame burning normally. If that sensor gets dirty or fails, the heater thinks there's no flame even though there is and cuts the gas as a safety measure. Cut the power, remove the cover, and check all the wire connections to be sure the leads are clean and dry and snug. The ignition sensor is near the bottom. If that doesn't work, then the sensor might be faulty rather than dirty. Call a tech to replace it.

Do the burners come on? If so then yes it probably is the flame sensor if not then there is another issue not the flame sensor. The flame sensor could just be dirty take the flame sensor out and clean it with a piece of emery cloth or lite sand paper and put it back in and this should get the burners to stay on.

dirty flame sensor try cleaning it or there is air in the line

make sure the flame sensor is connected good. If the terminals are dirty or corroded the board will not get the proper millivolt reading from the sensor. Also, remove the flame sensor and take emery cloth and clean the point where the flame sensor attaches to ensure a good contact point there.

Okay, what is going on. is the system lighting or not. If it is just sparking then you need to just the gas value. But if the system lites and then only have a flame for about five sec. then shuts back off, then your flame sensor is dirty. Take a wire brush and clean the flame sensor. The flame sensor is right there with the burns because a flame has to hit it for the gas to stay running. Just take a wire bush and clean it..... let me know