I got a call about year ago from a lady complaining that the pilot won’t stay on. A service tech from another company had been out three times. The tech had changed gas valve and thermocouple, but the pilot still keeps going out.
When I got there, I found a 10 year old Ruud furnace with the vent pipe not fully on the inducer draft housing and pilot vent tube sitting on top the furnace. I asked the customer what going on??? She said, the other service tech told her that the vent was clogged up with a bird nest. To keep the pilot on he had to leave the vent pipe that way.
I didn’t find any bird nest in the vent pipe, but did find wires jumped that went to flame roll out switch, pilot vent tube broken off from inducer draft blower housing and cracks in the heat exchanger.
I told the customer that the heat exchanger is still in warranty, but she wanted us to install a new furnace and do a much needed coil cleaning.