I have a Williams propane gas wall furnace. It is thermostatically controlled and it was working perfectly according to the program until suddenly it didn't. I removed the thermostat and connected the two wires. It did not fire. Leaving the two thermostat wires connected, I jumped the connection at the unit and the unit fired up and stayed on even though I removed the jumper wire(a paper clip). The unit ran for several minutes than went off whereby I jumped it again. I did this repeatedly(remember the thermostat wires are connected with no thermostat) for about 3 or 4 days whereby the furnace would run once jumped anywhere ftom a few minutes to maybe an hour. After 3 or 4 days I noticed that the furnace would stay on. So I reconnected the thermostat and again it worked perfectly for a few weeks and then suddenly it would not fire. I removed the thermostat once again, connected the wires and jumped it again and essentially got the same results as before. And once again after several days the heater would stay on. So again I reconnected the thermostat and again it is now working perfectly for several weeks. Of course I am expecting it to stop.
What could the problem be?