idiot DIY'er here :P. I recently installed a smart thermostat and long story short; I removed the two wires from my furnace's board for the external air conditioning unit in the process. I was going to put them back today, but found that the Y and C wires that are coming from it are not standard colors, so I am absolutely unsure which is which. I tried to look up some information on which is which before just connecting them and I found a few stack exchange postings on which to connect where, but no concrete "this goes there" info.
I have a few pictures of the connector from the outside unit with the corresponding wires which i am trying to identify and I think that the combination that I am looking at is as follows (connector->low voltage wire):
Y wire = Yellow/Orange->White
C wire = Black->Red
Can someone just confirm that I am correct with this based on the pictures posted?
Best Answer
Connect one to Y and the other to C -- it actually doesn't matter which one is which
On an ordinary air conditioner like yours, the Y and C wires going off to the outdoor unit connect directly to the coil of the compressor contactor (basically, a big switch that is turned on and off by an electromagnet). Since they carry 24VAC to the coil to turn it on when the thermostat calls for cooling, that coil is polarity-insensitive (it has to be to operate on AC, after all).
As a result of this, it does not matter which wire in the air conditioner cable goes to Y and which goes to C, as long as one goes to Y and the other goes to C, and they're both hooked to the contactor coil on the other end. So, go with your preference, or even flip a coin, when it comes to labeling!