I had a squirrel get into my attic and it completely chewed apart the connection between the 3 sets of wires between the thermostat, the furnace, and the A/C. The problem is I'm not sure how to reconnect the wires. When I've matched up similar colors between the wires, the fan and heat come on regardless of the settings on the thermostat so something isn't connected correctly. If someone can explain how to match up the wire colors, I'd be very appreciative. The system used to work correctly so these wires go together somehow. Below are the wires that lead to each device.

Thermostat Wiring (wire coming from the thermostat)
The thermostat wire has 4 colors: Red, Yellow, Green, White

At the thermostat itself, the connections are Rc-Rh-Red, Y-Yellow, G-Green, W-White

Furnace Wiring (wire coming from the furnace)
The furnace wire has 4 colors: Red, Blue, Green, White

A/C Wire (wire leading to the outside AC)
The A/C wire has 2 colors: Red, White

I've attempted the following connection which did not seem to work. All 3 Red together, All 3 white together, Green (thermo) to Green (furnace), Yellow (thermo) to Blue (furnace). When I did that, I had the thermostat settings on Auto (Fan) and Off (Heat/Cool). However, the furnace fan came on and the heat came on even though the thermostat said "Off". Thanks for any help.

 

i think you should move your post to the electrical wiring section you will get many responses there.

 

We need to know what the terminal markings are in the furnace where the wires connect and the same for the A/C outside unit.

Most likely the red, green and white leads from the thermostat connect to the same colors from the furnace. The blue wire from the furnace connects to one of the two wires from the A/C outside unit and the yellow wire from the thermostat connects to the other wire from the A/C outside unit. The wire colors to the A/C outside unit are probably not important.

 

I will try to make this as clear as I can but if you have any doubts or questions please post back.

Red from thermostat connects to red from the furnace.
White from stat to white from furnace.
Green from stat to green from furnace.
Yellow from stat to one wire from A/C (color does not matter).
Blue from furnace to other wire from A/C.

This is true for the VAST majority of the equipment out there. If things do not work as they should after making the above connections, it is likely some control has been damaged either by the squirrel or incorrect wiring.

 

Thanks all! Sorry it took me awhile to respond but I just got around to attempting your suggestions. You were absolutely right! I wired all like colors together b/t the furnace and thermostat and then connected to blue and yellow wires to the AC. Worked perfectly!

 

Glad it worked and that you let us know.

Now, fix it so the squirrels don't get into your attic.