Rewiring Old Coleman Furnace for Filtrete 3M50 Thermostat


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Old 06-24-13, 12:07 PM
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Rewiring Old Coleman Furnace for Filtrete 3M50 Thermostat

Hey guys, im attempting to install a new Filtrete 3m50 thermostat in my house but my old furnace does not have a C wire. I read several posts on how to jump the Y and G wire together and then use the old G wire for the C wire. Only problem is that I dont know exactly how to do that on my furnace. I have attached pictures of the furnace wiring. Any help is greatly appreciated.
 
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Old 06-24-13, 04:32 PM
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You have a red and white wire that go to the a/c unit outside. The white wire is wire nutted to a blue wire. The Red wire is wire nutted to a brown wire from the furnace. That is the C wire. The diagram says it should be blue though.
 
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Old 06-25-13, 09:35 AM
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Thanks for the reply Kevin, just so Ive got this right before I touch anything. Now could I just run a new 18/5 wire and connect the new 5th wire to the brown wire as well? or did I misunderstand that? And if the answer to that is no, would rewiring the G to a C be a better option? and in order to do that, would I move the green/yellow nutted wire to the red/brown nutted wire? If my darn furnace just had a nice labeled junction I wouldnt have this wiring issue haha
 
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Old 06-25-13, 01:55 PM
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Yes, run new wire, but I would run 18/8 for future upgrades. And then extra wire for C will connect to brown.
 
 

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