I've had an infrared propane ventless heater in my shop for over 20 years. Never a problem till this week. First of the week, we had highs in low 70's, so pilot was turned off. Thursday, low was to be in 30's, so heater need to be lit again. Lit pilot with no problem, but each time heater would come on, pilot would go out. Knew it wasn't the thermocouple, as pilot would stay lit till gas valve opened. Next thought was POL connector wasn't depressing valve on propane tank, as I had just changed tanks. Use gas valve adapter, and same results. Next thought was regulator had gone bad (yes they do,) so changed regulator, using existing POL connector. Still same results. Because I had an identical heater in storage, I changed heater out in case problem was in heater control valve shutting down due to defective oxygen sensor. Same results again. Finally changed out the POL connector, and new heater worked fine. Today reinstalled old heater and all is good. Seems that limiting device in POL connector had failed, limiting the gas supply. As always, enough detective work will find the problem. Thank God for the ability to trouble shoot problems.
