Why does pilot go out?

You might have a bad heat exchanger

-Sounds like bad thermal control switch.
Good luck

Mail

Try taping assembly the pilot with a screw driver sounds like a dirty pilot and when the flames come on the pilot pulls away from the thermal couple but tap it when the pilot is lit not the burners

Sounds like the pilot is mounted to far away from the burner. I have seen it happen before where the pilot has detached and the main burner will just keep pumping gas in until it hits the pilot flame and just flash flames and everything goes out.

Or it just could be a bad thermocouple that is going out all the time.

try cleaning the pilot sounds like its a short pilot and when the burner comes on it pulls the gas from the pilot light .

i'm thinking after the main valve opens the pressure could be dropping in the pilot tube. this could be due to a dirty, plugged and sometimes spider web inside the pilot tube. rare but does happen, nice warm home for a spider. good luck. if not let me know. could also be weak pilot coil.

Either the pilot light orfice is dirty, and you will need to pull it out and clean it, or the thermocouple is bad. If the pilot goes out as soon as you let the button go then it is most likely the thermocouple. If the pilot stays lit for a few days or hours then you will need to clean the pilot orfice, heres how:
1 turn off the gas supply
2 unhook the main burner gas line from the thermostat, this is the line that goes to the burner
3 unhook the pilot supply line it is usually next to the main burner line
4 unhook the thermocouple from the thermostat
5 remove the burner assembly
6 take the orfice out of the pilot line and clean it out by blowing thru it, use an air compressor if needed.
7 reassemble and light pilot

sounds like your thermacouplar is going out and needs replaced. Sometimes these will act like they are working fine , but when the pilot stays on for awhile and later goes out it is a sure sign that it is bad

take millivolt reads while main burner is on.i suspect you will see a drop in voltage until you get to point where it will no longer operate burner(around 200mv).if this is the case you probably have poor pilot characteristics due to dirty pilot,pilot out of adjustment ,obstruction or insufficient gas pressure

Your unit has a "vent safety limit switch" which is a high temperature limit. It gets hot enough to trip over time because you do not have proper venting. It is a safety switch and SHOULD NOT be disabled - instead find and fix the venting problem(chimney bad?)!