About a month ago the pilot light on my gas furnace started going out occasionally, perhaps once a week. It's an old gas furnace with a solenoid gas valve with pilot light and safety thermocouple. The sheath on the thermocouple was burned through so I figured that was my problem. I replaced the thermocouple. Then the pilot light started going out every couple of days. I played around with several thermocouples and it appeared that the particular thermocouple affected how often the pilot flame went out. So, I replaced the gas valve. This made absolutely no difference. I then decided that the problem was either an intermittent electrical fault or an intermittent gas supply problem. Changing thermocouples and the gas valve should have cleared up an electrical problem and the fact that my gas water heater never lost its pilot flame seemed to argue against a gas problem but I removed and cleaned the pilot flame burner and gas line. This did not help. I decided I had better see what was happening so I selected the worst thermocouple, one that failed every few hours, made a pot of coffee and sat in front of the furnace. Well, I got lucky. What was happening was that the pilot flame was being blown out. When the thermostat called for heat, the gas valve opened and the main burner came on. As the heat exchanger got warmer, the draft past the pilot flame increased until it blew out the flame. I tried adjusting the pilot flame but that didn't fix the problem. I checked the heat exchanger, flue, and chimney. They all appeared to be normal. I then removed the burner assembly and cleaned it thoroughly. This had no effect. I then removed a baffle that covered the top half of the air inlet into the heat exchanger ( it covered part of the ports that the burners fit into. This has apparently fixed the problem. However, I'm uncomfortable with this modification on my furnace. What suddenly changed to cause this problem? Is there something beside a 30 mV thermocouple that I should be using?

Our home needs some additional ventilation. It is too "tight" and we are having some condensation problems on windows and floors. An air-to-air heat exchanger has been recommended to us, as has just cutting some holes in the ductwork. Your educated thoughts would be welcome!