Built in Propane Heater thermostat not functioning

I found some info on your unit on the net. It showed the sensing bulb mounted horizontally with a clip somewhere at the bottom of the unit. Also, just be aware that the bulb assy won't react as quickly to temp change as your standard t-stat. It appeared by the literature I saw that the sensing bulb was located where the incoming air to be heated would have to pass over the bulb itself, even though it isn't a fan forced heater. Good luck.