Recently I replaced an old mercury thermostat with a programmable digital model (a PRO1 T955W).
It is set to operate in Heating mode. The desired temperature is set to 70 and the in-home temperature is in the low 60s. Yet, the oil-burning furnace does not turn on. As soon as I touch the LCD screen, its back-light turns on and shortly afterwards the furnace motor starts running/burning. Then after a few seconds, the LCD dims, and the furnace stops before the desired temperature was reached.
I was initially wondering if I might have switched around the R and C connectors. The thermostat only has those two inputs. After switching them again, the same problem persists.
Here is a picture of the wiring. It shows the R & C wires. The insulation looks a bit worn. I have made sure that both cables are securely screwed into place. Picture of Wiring
Here is a picture of the back side of the thermostat: Picture of backside
Here is a picture of the thermostat display when connected. Here the display is lit (after I pressed the display), and the furnace immediately turned on. As soon as the display dimmed (after a few seconds of not touching the display), the furnace stopped immediately. Picture of thermostat display