The low temperature alarm went off last night at 11 am. I was in a deep sleep. It was supposed to go down to 33 but only went to 39. The outdoor temp when the alarm went off was 41. Tried swapping sensors with the good heater but no dice. The heater starts uo but quits after a few minutes and then won't restart. I cranked up the porch temp to 70 and turned the fan on full blowing hot air from the top of the hot tub into the greenhouse. This morning when I woke at 7 I tried jumping out the flame rollover sensors and all worked well. I read online that on some heaters the upper rollout sensor was prematurely tripping. Tried the upper then the lower sensor individually. Either sensor by itself causes gas valve shutdown. For now I removed the rollover sensor. It's the end of the heating season so there is no rush to get a rollover sensor in there. I will probably put one back in mounted on a bracket away from the flame but close enough to detect anything bad in the firebox. Cut the bench legs while listening to Don Giovanni on the met Saturday broadcast. Installed the Northernmost bench and moved the half bench inside and placed it on top temporarily until I cut proper legs for the upper bench. I'm pretty tired this afternoon! Dinner was ribs, brown rice, broccoli and Melbac wine. Tonight is Daylight Savings switchover, we went to bed early but I read a little more of Jules Verne.