Hi all.. I did a search to see if this problem had come up, but nothing matched my wiring. Stupid dog! ;)

From the thermostat, I have a 3-wire section (green, red, white) that leads to the compressor outside my house. I looked inside the compressor and only found blue and yellow (heavier gauge strand) wires. I'm guessing I only need to connect two of the wires back, but the colors don't match up. What do I do? It's an older Trane XE 900.

Please! Any info would be appreciated. Its getting hot! :eek:

If you have a volt meter and those are the only 3 wires going to the comp[ressor, with the thermostat set to cool, check the red, green yellow for a pair with 24 volts AC. If so, just connect them either way to the blue and yellow. If not, it will be more complicated.

Usually there is a 24 volt AC transformer in the furnace with the secondary winding connected to a red wire running to the thermostat and a blue wire, common, to the gas valve, A/C relay, and fan relay. From the thermostat there will be white wire to the gas valve, yellow to the A/C, and green to the fan. The thermostat is wired to switch the power from the red to the white, yellow, and green as needed with the blue completing the circuit. Most thermostats and furnaces have the contacts labeled R, B or C, W, Y, and G for the corresponding wire colors. It may be wired to have the A/C control wires return to the furnace and its controls and then a second wire goes to the A/C unit. Internal wiring may replace the green wire if the thermostat does not give you the option of fan only or continuous fan. Digital or programmable thermostats may need the blue wire connected to them.

You may have to pull the thermostat off the wall and identify which wires are connected to the Y and B or C terminals. Then connect those wires Y terminal to the yellow, and B or C to the blue.

When you are done, you deserve a laugh. See https://www.askmehelpdesk.com/showthread.php?t=11141

Sorry.. I'm not very good with electrical work.

I edit the above to show that the 3-wire is Red, White and Green.

I also took some pics (not very good ones) of the problem. I don't have a volt meter handy, so I should probably wait until I can get my hands on one.

http://darren.bombs-away.net/wiring/

Thanks for the help... I fixed it per your instructions. :)