I have a picture of the furnace switch board here.
http://pg.photos.yahoo.com/ph/laynev...&.dnm=f165.jpg

Had an air duct company cleaned duct yesterday and found out the guy made a mess. 3 wires in the furnace switch are loose. Gas furnace model is 58GS075-GA (CA?)

RED and GREEN wires from the thermostat.
CLAY (WHITE?) wire from A/C.

I put the thermostat wires back as RED ->RED, GREEN ->GC. The furnace seems working OK. But how about the CLAY wire from A/C?

On the switch board I have: C, Y, GC, GH, R, W.
The red wire from A/C is connected to Y on switch board.

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I was guessing GC is Green Cool? Should I connect the CLAY from AC to GC, and the GREEN wire from thermostat to GH (Green Hot?).

I'm totally new and would appreciate any help.
-Layne

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 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. It may be wired to have the 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.

The picture helps. Do you know where the heavier red wire on the left now connected to C goes? I suspect C is the common with the gas valve and fan relay connected to it internally. If you can find either of them check the second wire, not the white or green and see if it connects to C. You can also check to see if it connects to the opposite terminal on the transformer from the wire that connects to the R, red. If the furnace, fan and all, work right, you have the red, green, and white from the thermostat connected correctly. If you unscrew the C terminal, you may find the broken off end of the clay wire.

I sort of feel the duct cleaning company should be told come back as straighten their mess. On the other hand you may be better off fixing it with my help than letting them make a bigger mess.

Thanks Labman. Problem solved.

I complained to the cleanning company and was told to wait for their tech guy call back. And you are faster replying. What a shame for them.

The Thick Red line does go back into the back of furnace. I can not tell where it goes.