OK I have an old honeywell round mercury thermostat that is connected. Ive read all the wiring help tips on several sites. I have taken the old one off carefully and looked for terminal markings and there are none. Not so good is the fact that I have 4 wires. Red and yellow jumped together and green and black jumped together. No white wire. No markings on the old terminals for letters at all.

The furnace is an oneida royal loa, the new honeywell thermostat is heat only and has a spot for the w r y wires but that doesn't help me, I have and it is a model ct87k. The wiring instructions are great. But guess what no white wire so I'm clueless. Why do I not have a white wire.