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Need help rewiring thermostat to furnace connection -- squirrel chewed wiring

Need help rewiring thermostat to furnace connection -- squirrel chewed wiring


Old 05-11-07, 03:49 PM
Thread Starter
Join Date: May 2007
Posts: 3
Need help rewiring thermostat to furnace connection -- squirrel chewed wiring

I was told to move this post here from the Heating forum.

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.
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Old 05-11-07, 04:18 PM
Join Date: Mar 2006
Location: Wet side of Washington state.
Posts: 18,372
The heating forum was the correct place and here is the answer I posted last night.

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.

Hopefully with all of your random wire splicing you didn't blow the fuse, or worse, transformer on your furnace board.

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