I have a oil heat only system with two wires- one green one white. After hooking up the White to the 'w' and the green to the 'g', and setting the programs, I woke this morning to a really cold house. I tried resetting the thermostat by removing the batteries, but even after overriding the program by advancing the heat, the furnace still did not kick in. Not until I switched the 'fan' from 'auto' to 'on' did the furnace start running.

I have two Qs- 1) The insulation on the wires is cloth, and I wonder if the colors have changed with time? And 2) Should the fan setting just be left in the 'on' position? And if so, will the furnace or the blower shut itself off ever?

Thanks!