I have a 1974 mobile home with a international thermo corp furnace mac 1199 / ser #n1199mac71 nov 24-05. We have replaced the thermocouple, valve, and blower - the pilot light- lights and runs for 10 minutes and shuts off for 10 and then runs like that for about 24 hours then the pilot light goes out and blows cold air and will not shut off. I do not have a down draft to blow it out. Do you have any idea what this could be I'm at my "wits end" ! Thank you