I have an older floor furnace thats pilot light is on but will not kick in and light to heat. I have jumped the thermostat and it heats sometimes. I jumped the connections at the furnace and it kicks in most of the time. I changed out the thermostat and it controls it to turn off the furnace once I jump it at the furnace control but then will turn it back on. I had someone come out and he said he changed the pilot generator control and it worked at the thermostat for about a day then began this same problem. Any ideas please?