Replacing Thermostat - no labeled panel on furnace?

lifesupport4uJuly 28, 2014

I replaced my home thermostat with a wifi system. It works great.

A friend asked me to do the same. He has an old analog thermostat (no digital display) and a 4 wire system.

However, at his furnace the wires are all spliced and appear to run to various places. I could not find one labeled panel like mine had.

My understanding with a 4 wire system is you have to jumper the fan wire. I am not sure how to do this without a panel.

Any advice or help would be great.

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Is his system a combination heat/AC unit? The typical four wires on a 24v controlled combination system are:
Red (power)
White (heat control)
Yellow (cool control)
Green (fan control)
The thermostats I've used in my last three houses have not required any type of separate jumper, although some thermostats may have had that function built in.


    Bookmark   August 1, 2014 at 6:05AM
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Does this thermostat need a C connection? Here a YouTube video explaining how to use the G wire as the C wire. The C (common) wire is the ground connection. You will have to find this connection at the furnace.

Here is a link that might be useful: Substitute G-Wire for C-Wire -- DIY Installation

    Bookmark   August 1, 2014 at 8:34AM
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I do need to substitute the G wire for the C wire like the video above.

The problem is "finding the connection at the furnace" as you put it.

Most furnaces seem to have a panel where all the wires connect to the labeled terminals. This furnace does not have labeled terminals and the wires seem to be connected directly to different parts on the furnace.

    Bookmark   September 21, 2014 at 11:48AM
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This is a very basic wiring diagram. Hope this helps

    Bookmark   September 21, 2014 at 12:18PM
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How do i wire a nest or honeywell wifi thermostat to to that ?

The old thermostat was analog (no digital display).

    Bookmark   October 9, 2014 at 12:15AM
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