I have an older ge furnace that I can not figure out the wiring for fan and limit switch. There are 3 wires coming out of the switch. The red one marked limit goes to the 24v trnsformer, the green wire marked fan goes to the furnace sequncer. The other wire is black and unlabeled. Were does this wire go? I have hooked it up to 120v power and the fan runs all the time 120v power is on, even if thermostat is not call for heat. The unit does not have a wiring diagram on cover of unit. Could the black wire go to power and the fan and limit switch be bad? Thanks for the help. John