Lock out from loss of flame?

[teamg]

I turn down my furnance during the day from 70 to 60 and when i turn it up in the evening it heats for about 2-3 degrees then blows cold.  So i look at the code and its 8 blinks which is a lockout from flame loss. I have not touch anything it just started doing it about a month ago any suggestions?  Thanks

[Admin]

Is this a York or Coleman?  I would remove and clean the flame sensor.

[teamg]

Its a Coleman Evcon and I will try cleaning the flame sensor. How expensive are they should I just replace it?

[Admin]

No need to replace the flame sensor, I use mesh plumbers paper to sand the rod clean.  Avoid using sand paper.  There could also be a problem with the grey ignition module.  You would need to measure the micro amps on the flame sensor. 
If that furnace has an upshot burner you should remove it to clean the sensor.  Take a pin and clean the burner orifice as well.