I have been looking over the forums the past couple of days and have tried some things.... Here is the problem, The furnace goes on, the big house blower starts up, 45 seconds or so the the small blower in the furnace starts up, then the glow plug lights up, the flame ignites, and it runs for 2-3 hrs. Then I notice cold air coming through my vents, go check the furnace and the flame is out but the furnace is still blowing air. I look at the thermostat and the house is not up to temperature yet. The code blinking is 13, I thought that the problem could be the limit sensor so I replaced that last night. I had the same problem this morning when the heat came on in the morning. To get the heat back on i can hit the manual reset button, turn off the power to the furnace, and then turn it back on. Everything will work right and turn off the way it should if it doesn't have to run for a long period of time (hits the temp it should on the thermostat). I sometimes get a code of 33 but after I reset everything it goes away as well. The air conditioning on the unit works perfectly fine, just the heat thats the problem. Things I have checked: New filter furnace exhaust to the outside(blowing air out, not a lot but can feel it coming out. don't know how much should be coming out.) limit sensor (new one) the flame is blue, no yellow or any other color the returns are all free of constriction or being blocked Any help would be much appreciated. Thanks, Chris

I cannot find an answer for this specific question anywhere! I live in a rental with a 35 yr old Williams 3509622 wall heater. When I moved in I replaced the broken Honeywell dial thermostat with a newer digital one. I got the pilot going, turned it on, and heat! It worked great for two weeks until we had a big rain and wind storm. That night I noticed it was getting increasingly warmer than what I had the thermostat set for...then all of the sudden the heater shut off and hasn't worked ever since. I can get the pilot lit, but when I turn the thermostat to 'on' there is a loud click and the pilot goes out. Jumping the thermostat wires also produces the click and then the pilot goes out. I put in a new thermocouple/generator and cleaned the pilot orifice but still no heat. The pilot will not stay lit if I start this process with the thermostat in the 'on' position so that's a no go. My landlord says that there is a cap on the flue making it unlikely debris is down there, however I'm inclined to believe that it's some sort of malfunction due to overheating because of the temperature increase the night it died. Here is where we are at odds.. The unit has a limit safety switch on the top, left hand side. This is connected to two black wires that connect to the gas valve. The current model of this heater uses a switch with a red reset button. The safety switch on this very old model does not have a reset button. I believe that this means if it was tripped during the storm, it has to be replaced. My landlord believes the pilot wouldn't stay lit if there was something wrong with the safety switch. He says our safety switch without the red button is 'self resetable.' Is it not possible that this is dead? They do sell them as replacement parts.. As a side note, the serial number is no longer visible on the heater. When I called the Williams Company they told me that without that, they cannot give me any specs as to the millivolt system and that I cannot rely on the current manual because things will be different in my unit. The replacement generator I purchased is a universal replacement for 600/750 millivolt pilot burners, but I don't know if this was the correct choice without having more technical information.