When A/C kicks on so does Gas Furnace...


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Old 04-26-09, 03:13 PM
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When A/C kicks on so does Gas Furnace...

When I turn on my A/C unit it seems to also turn on my gas furnace (I have an outdoor A/C unit). I have switched out my thermostat and everything and it still does it. I am getting warm air return.

I can manually turn off the gas flow to the furnace but get a clicking noise (suppose from igniter) and it does appear to cool the air, but that can't be a good thing for my furnace so I don't do it. I did during the winter have my motor replaced. Could they have miswired the furnace or do I have a bad control board. What can I look at quickly to see if they wired it incorrectly? I followed the color schematic and I could not find any mistakes.

Thanks in advance.
 
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Old 04-26-09, 04:07 PM
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if you turn the heat on does the AC run?if not then somethings up with the control board.the motor wiring is not control voltage as on the thermostat wires.pop the stat off the wall and disconnect the W wire and tape it then tuck it in, and put the stat back.....if your not planning on using the heat. shutting the gas off during heating call will not stop the cycle call to heat only after several attemps to spark the pilot.your Y wire and the W wire should not be connected anywhere on the system either up on the stat or in the furnace check those 2 colors.
 
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Old 04-26-09, 04:25 PM
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Okay I tried to disconnect the W but still the furnace kicks on with A/C. I did just try to turn on the heat and noticed that the outside A/C also turned on. So now what? Does this mean it is hooked up incorrectly?

Thanks
 
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Old 04-26-09, 05:22 PM
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Look at the box for the thermostat. Sounds like you may have gotten one for a heat pump. They did this at my mother's house one time.
 
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Old 04-26-09, 05:59 PM
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I looked at the thermostat and I have it set as Non-HP, so that should not be the problem. I guess that I should have stated that it was working previously for the past 2-3 years.
 
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Old 04-26-09, 06:09 PM
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if you disconnected the W up on the stat and the heat still ran with an AC call the Y-Yellow and W-White are crossed....... touching...jumped,down on the furnace board disconnect the White wire where it lands in the furnace then try the AC,if you just get the AC the W is rubbing with the Y.tape off the White-W wire in the furnace.you need to pull a new brown bundle(8 wires)between the stat and the furnace.
 
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Old 04-26-09, 06:36 PM
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Okay...Wow that WORKED, Sminker!!! The A/C is on and the furnace is not. So, the yellow was touching the white.

So, is it safe to leave the white wire unhooked for a couple of days from the furnace. The gas isn't flowing or anything right.
 
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Old 04-29-09, 03:19 PM
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thats COOOOOOOL sure you can leave the white taped away for now it is just you won't get any heat for now.do you have any spare wires in the bundle from the furnace up to the stat...if you have any even just one there just use that as your HEAT wire "W" .shut the furnace toggle and change the color up at the stat and down at the furnace and repower.there is no code for thermostat wires and what they connect to ,they are just industry standards for a tech walking in to do service.just make sure that white is taped away at both ends because it is HOT with 24Vs when your in cooling.
 
 

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