darren

Hello
I have a Lennox furnace(not sure of the model number, can be found if needed) but every year about this time it acts up and by reading the flashing lights it says to check the flame senser. So i pull the flame sensor out sand it and take off the blue markings(to make it look like new), put it back in and will work good for another year.

Is this a normal thing to do with a flame sensor and how many times can i do this with out ruining the flame sensor.

Thanks for your help
Darren

HVAC Doc

Depends on the air quality where the furnace is located. High chemical (laundry rooms) or damp areas (leaky basement) can cause flame sensors to become dirty. Impurities in the gas delivered can also be a factor. Manufactures are now recommending using a fine steel wool over sandpaper due to the silica content and residue left on the sensor.

Bestheating

Doc's advice is good, but let me add the following thought. Flame sensors read the current from the actual sensor to the nearest ground. The connection is the gas itself. When the flame sensor is cleaned, the job is only half done. In your case, I suspect you may have an integral pilot assembly and the sensor is sensing the pilot flame. The other application is to sense the main burner flame. In either case, a good clean ground is of utmost importance. Take out the pilot assembly hood, or ajacent burner, whichever is the case and brush it with a wire brush. Also, if it is the pilot sensing type, make sure the pilot orifice is clean and giving you a good flame. This is quite common. Flame sensors are not that expensive, and I have been replacing them more often lately. Cleaning them is not always effective.
Larry