Ever since he left no heat. The furnace runs fine for a day or so.

How To Figure Out What Is Wrong With Your Furnace Dengarden
Flame rollout switch keeps tripping. Replaced filter opened all vents returns not blocked checked combustion air intake and exhaust and they are not blocked. This happens because the flames are not being drawn into and through. Unfortunately in most cases a tripped. This rollout switch that keeps tripping sits right on the metal above the burners. Inspected burner nozzles and they look good they are only 3 yrs old from when furnace was converted to propane only thing i can see is that there is a bit of residual flame around the ends of the tubes that feed the heat exchanger. I reset it and it tripped again.
I can reset it and the furnace will function fine for about 30 to 36 hours my furnace flame roll switch keeps tripping. The jet of flame does not completely shoot into the heat exchanger the box containing the propane. Flame roll out switch keeps tripping on my rheem. Published on oct 10 2018 one common symptom of a failing or blocked heat exchanger is the roll out switch tripping. In this video i explain what the flame roll out is why it trips and what you would need to do next. If the furnace limit or rollout switch senses that over heating occurs then it trips the rollout switch to prevent an unsafe over heating condition.
I had a service technician out for yearly maintenance on my gibson kg7sc earlier this week. I have not seen any flames coming out of the exchanger intake it just appears to be 3 nice blue jets of flame blowing into the intake on the exchanger. Just resetting the switch and going on is like turning off a fire alarm and leaving the fire burning. Is the flame roll out switch tripped in your furnace. I can reset it. The flame roll out switch is a safety switch that shuts the furnace off if flames come out the front of the furnace.
Now if it does it. My furnace flame roll switch keeps tripping. He found no real problems but did say some of the intake and exit pvc piping wasnt properly glued so he fixed them. So this other company closed some holes of the topmost burner so that the flame doesnt fan out as it does for the burners below. The flame roll out switch. The flame roll out switch tripped.
Flame rollout on side keeps tripping. That has created another problem now. If flames roll out the front of the burner its a strong sign. Roll out switch keeps tripping. The switch is not the problem it is a symptom of a very serious problem. Tripped rollout switch anytime you have to reset a rollout switch on a furnace warning alarms should go off in your head.
I noticed that there was some rust hanging down from the top of the intake where the flame shoots into and so i cleaned this off and i watched it and there was no flame roll out.