I have a Carrier Gas Furnace. I believe the model is 58CTA or 58CTX (not sure which one).
The thermostat I have is "White-Rogers" Model 1F86-0471. We have NO A/C unit.

The heating works fine (in the winter)... when it is cold - the furnace turns on, and flows nice warm heat around the house.

In the summer, the basement is much cooler than the main floor, and I would like to have my furnace circulate the air in the house by setting the thermostat fan option to "ON". Problem is that the fan does not turn on. I have the black white going to the RH terminal on the thermostat, which is daisy-chained to the RC terminal. I have a white wire going to the "W" terminal on the thermostat. That is it.

The furnace seems to be a decent one based on my research, and the thermostat seems to have the options to make this thing work... my assumption is that I'm missing a wire. IF I had to guess, I would think that there should be a wire that goes from the furnace (somewhere, upstairs to the thermostat and get wired into the "G" relay (terminal) - which is the fan relay.

Mr Expert(s), what do you think? Its 26 degrees upstairs right now and 20 downstairs.. any advice?

If you power up the G terminal in the furnace the blower will run. If you use the G terminal on the thermostat and run a wire to the G terminal on the furnace the blower will run. No problem if you have a extra wire in the thermostat cable you can use for this purpose if not you will have to run a new wire. Or as I said before you can just put a jumper to the G terminal and the blower will run. The down side to this is whenever you want to stop the blower from running you will have to go to the furnace and disdconnect the wire to the G terminal.

Just so I understand you correctly, I would need to run a new wire from the furnace to the thermostat? Or are you saying that I can put a small wire from the W to the G terminal on the thermostat? Again, I want to be able to set the thermostat to ON and have the fan blow (no heat), and when I set back to AUTO it will only run when the thermostat calls for heat. I'm pretty green at this stuff so I just want to ensure I understand.

Thanks

To get it to work like you want you will have to run a additional wire from G on the thermostat to G on the furnace. This will allow the thermostat to activate the blower circuit in the furnace when you put the thermostat lever to ON for the blower. When you turn the lever on the thermostat to AUTO then the blower motor will only come on when heat is selected as it has always done before.

Thanks very much for the help - sounds like I will have to have a qualified person come in and help with that.