When i lite the pilot and turn up the temp. the burrners light and the blower comes on. When i turn the temp down the pilot goes out. this happens two out of three times? I have already replaced the thermocouple. It seems as though if i leave the burners on for aprx 10 min. the pilot stays lit when i turn the temp down. However if i turn the burners on then quick turn them off the pilot goes out. Any thoughts?
Say what brand ,style & model of furnace you have.
The Pilot orifice may be dirty, meaning that the pilot flame is soft enough to be affected by the natural draft which is pulling its flame away from the thermocouple. Watch the pilot flame to see if it is being pulled or pushed away from the thermocouple at any point in your heating cycle.
Concussive ignition or shut down of the main burners knocking out the pilot.
Lots of possibilities.
Doing a closed thermocouple test with a dcmv thermocouple adapter is the usual first step.