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Heating, Air Conditioning, Fridge, HVAC/Wiring new furnace to old condenser


I just installed a new Goodman furnace and I have three wires coming from my old condenser. I beleive one of the wires go to my Y terminal and another to my common terminal but im not sure why I have another wire. Im getting 18volts on the wire coming from the transformer in the condenser unit and 5volts coming from the two other wires that go to my contactor. what would be the right wiring configuration.Condenser is an older GE.

Well, it really depends on what kind of cond. unit you have.  If you have a heatpump, then you will need a min. of three wires.  One wire is Y, one wire is common, the last would be for the rev. valve. Cond. unit need a min. of two, but other may have a control board or other things that might require a third (hot)wire.


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Craig HVAC Expert


I have been in the HVAC field for the past 18 years. I can help with most HVAC questions. I work on commerical buildings for the most part, and have yet to find anything I could not troubleshoot and repair, when repairable. I work on small 1 ton units to a 2500 ton chiller. Troubleshoot air flow, elect, and control problems. I attend regular classes to keep up with the latest and greatest.


I work on commerical sites, hospitals, gov't buildings. I can troubleshoot just about anything in the HVAC business.

5 years trade school, VFD training classes, Liebert factory training, some York and Trane factory training.

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