If the wires to the thermostat are large like outlet wires, you will need to have these replaced from the power source to the thermostat location. And you may exasperate the problem which will cost more in the long run. This power wire is necessary to complete a two-stage firing of the furnace. In the case of heat, it instructs your furnace to open the valve supplying gas. If you cannot get it to work correctly then it is best to call an HVAC tech who is good with control wiring. It is very possible they have a solution for you. This thermostat wiring diagram is a split system.
Or are there thermostats that can control the 3-position gas valve?
How to Attach Wiring of Your Heater Thermostat to Your Furnace
If the thermostat is not working properly, you may find that your home is colder or warmer than you would like it to be. Modern furnaces use a control board that usually is based on a time increment for both the starting and stopping of the fan when in heat mode while older furnaces used a mechanical type of relay call the fan limit control that control the fan based on the temperature in the heat exchanger. Is there a way of finding out what the HVAC current condition is, based only on the wiring voltages? Repeat the replacement process for the W wiring to complete connection for any W2 wiring if necessary. GAA on December 11, at 1: