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  1. #1
    Join Date
    Jun 2011
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    Central AC not receiving signal from furnace

    I have an American Standard (I believe Trane makes it) Freedom 90 with the intell ignition board. About a week ago, my transformer went on it (10 yrs old) and I replaced it and got everything back up and running (thermostat lost power).

    I'll be installing a 3amp inline fuse to prevent this from happening again.

    Yesterday I got home from work and noticed the blower was running on my furnace but the AC was not on. Grabbed my meter and started testing.. I found that the AC is not getting the 24v signal to power on.

    I unhooked the green wire and connected it to the hot/Red wire and bam, AC fired right up so right now I'm bypassing it until I figure out what's wrong. I know the AC will always run so I'm using the emergency shutoff switch temporarily to control power. With having a 9 month old and temps in the 90s, I needed to do the work around 1) for testing and 2) to keep her somewhat comfortable.

    Opinions on what you think may be wrong? Being that the wiring is ok from the thermostat to the furnace and from the green wire to the AC outside, leads me to believe the board is bad.

    Thanks for any insight.

  2. #2
    Join Date
    Dec 2001
    Ocean Pines, MD
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    Sorry, this is not a DIY area. It sounds like you had better get someone qualified to look at your system.

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