Furnace on with A/C - Round 2 - http://www.hvacmechanic.com/ Forums
Original message
| larryg
 |  "Furnace on with A/C - Round 2"
, posted Fri 18 Jun 21:36  
I took the white wire off the honeywell thermostat and turned
on the A/C to test the thermostat as you suggested. As soon as I turned it on I heard the inducer start for the furnace so I shut it down.
Pulled cover off of IFC and LEDs are all off. Furnace is a Rheem Criterion II. Can it be anything other than a bad IFC?
LarryG
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Replies:
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| cesarin78801
| "Re(1):Furnace on with A/C - Round 2" , posted Fri 18 Jun 23:09
look brother:
disconect all the wires from t-stat and put the red wire to white wire together and see if the out door unit starts.if the out door unit starts if it does that will be your cooling wire
then try red to green and see if the blower motor starts in the indoor unit then try red and yellow to see if the heat starts if it does that is your heating wire.now the wiring from the t-stat to furnace should be
thermostat-------------furnace
R-----red-------power-----R
Y----yellow----cooling----Y
G----green--blower--------G
W-------white-heat--------W
you might have the White wire hooked up at the furnace mistaken for yellow wire some color blind techs will do that hope it helps
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| | larryg
| "Re(2):Furnace on with A/C - Round 2" , posted Sat 19 Jun 09:17
The system was working fine for a year. No techs were in here on any service calls doing anything. The wiring is the same configuration as it was when it was working fine. Has to be something else other than a wire on the wrong terminal.
LarryG
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| | Xenos
Webmaster 
| "Re(3):Furnace on with A/C - Round 2" , posted Sat 19 Jun 16:40
May I ask what the origional problem was or is?
BTW the white wire should be heating.
Xenos.
The best way to escape a problem is to solve it.
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| | larryg
| "Re(4):Furnace on with A/C - Round 2" , posted Sat 19 Jun 18:36
LarryG
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| | LarryG
| "Re(5):Furnace on with A/C - Round 2" , posted Sat 19 Jun 18:50
Xenos
The problem is my heating/cooling was working fine until Thurs. nite when I noticed the furnace on with the A/C. You suggested testing the thermostat.....remove white wire and run the unit; if the furnace comes on, it's not the thermostat. Well, the furnace came on so it looks like it's not the thermostat.
I posted the results of the test on this forum and someone suggested doing tests to verify if the thermostat wiring was correct based on the assumption that someone could have worked on the system and mixed things up. No one has touched the system, so I see no sense in verifying if wires are connected correctly. I suspect the IFC.
I have a master electrician friend who trouble shoots stuff at a hospital comming over in the AM to help do some old-house wiring. Although not a HVAC guy, he could check out anything you might suggest.
Thanks
LarryG
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| | Xenos
Webmaster
| "Re(6):Furnace on with A/C - Round 2" , posted Sat 19 Jun 19:02
IFC ? Indoor fan contactor ? “furnace on”, you do mean the heat right ? Something is not making sense, open up the furnace and disconnect the low voltage wire connected to W, if the furnace still runs in heat I think you looking at a new control board.
Xenos.
The best way to escape a problem is to solve it.
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| | LarryG
| "Re(7):Furnace on with A/C - Round 2" , posted Sat 19 Jun 19:46
Xenos
IFC is "Integrated Furnace Control"......circuit board. I'll check it out tomorrow with my bud as you suggest and let you know.
Thanks for the help.
LarryG
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| | Xenos
Webmaster
| "Re(8):Furnace on with A/C - Round 2" , posted Sat 19 Jun 19:53
Of course that what it was. Didn't I say that. LOL LOL LOL
Xenos.
The best way to escape a problem is to solve it.
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