Not sure if anyone can help with this but why not give it a try....I have a propane Comfort Glow vent free wall heater. The pilot will light but when I turn up the gas the unit will light and stay on for about a minute then it shuts down, pilot and burner. I have tried two new tanks of propane and get the same results. Could I have a bad regulator or would it most likely be a bad valve. If I relight thepilot and then turn on the unit the same thing will happen....on for a little bit and then everything goes out. Thanks for looking.
you may have what is called a standing pilot ..it stays on all the time and the sensor.. thermocouple/thermopile ..has to verify that pilot flame is on...try to observe the pilot while the unit is on..you may see that the pilot flame is diminished/distorted after the main gas valve opens and establishes main flame..then once the blower fan comes on ...if you have a cracked heat exchanger..the air pressure can blow out the pilot flame causing it to turn off the gas valve...similar can happen if gas pressure too low OR sometimes from excess draft which can cause pilot to lift off thermocouple/thermopile
if you can turn blower fan on manually..hold a piece of tissue or lit match above burners to see if they get blown around ,,if so, cracked heat exchanger..would have to be replaced
there is an oxygen depletion sensor which apparently is problematic in that if it does not sense enough O2 it shuts off the gas valve..it is built into the gas valve and it may be cheaper to just replace the whole heater rather than trying to repair